I've been replacing my home network with Unifi.
You can run the cable from your existing upstairs router to the basement switch.
Then run a short cable from the switch to power insert-er (powers the AP) then a cable to the AP.
Then
There is a little setup on the AP. Download the Unifi controller and install.
The below was taken from https://www.stevejenkins.com/blog/2015/09/how-to-install-a-ubiquiti-unifi-access-point-pro-uap-pro/
Configuring the Ubiquiti UAP-PRO
Remember when I said the UAP-PRO was not a consumer device? Here’s where that becomes an issue. The UAP-PRO doesn’t have its own a web interface to configure, so you have to install a piece of software called the UniFi Controller on one of the computers that’s physically connected to your local network or existing router with an Ethernet cable. You can download the UniFi Controller software (for Windows, Mac, or Linux) directly from Ubiquiti at this link.
You won’t need to keep the UniFi Controller software running all the time, but you will need to have it running to set up the UAP-PRO, or change any settings later (don’t worry… you probably won’t have to change anything later). I recommend running it on a desktop system, and again… it must be connected via a network cable to the same physical network as the UAP-PRO.
After downloading and installing the software, run it. It will take a minute to initialize. It’s actually setting up a private web server on the local computer that you’ll access with your web browser. When it’s running, it will prompt you with a button to “Launch a Browser to Manage Wireless Network” to access the Controller.
Your UAP-PRO will be in a condition called “Awaiting Adoption,” meaning it hasn’t been “adopted” by (or added to) any network yet. If the UniFi Controller software “finds” the UAP-PRO right away and attempts to adopt it, great. Just follow the steps in the wizard to get up and running: along the way you’ll have to create a new admin user and password (this is only to configure the UAP, and not the same thing as the network name or password required for devices to join the WiFi network), and you’ll answer some questions like what network name you want to use, what password people will use to access the network, etc.
But if the UniFi Controller software doesn’t find the un-adopted UAP-PRO, don’t worry. It didn’t find mine right away, either. Just keep hitting “Next” or “Skip” to get into the main Dashboard area of UniFi Controller. Once in the Dashboard, click on the Devices icon in the left column. If you see a UniFi AP Pro in the list waiting for adoption, go ahead and hit the ADOPT button. If you don’t see anything, look near the bottom of the screen and click the Settings icon. Then click the Controller menu item on the left side, and make sure “Make controller discoverable on L2 Network” is checked. Hit APPLY then the X at the top of the screen to go back to the Dashboard. Now go back to the Devices icon and see if your UAP-PRO is there yet. If it’s not, check all your connections, make sure it’s powered, and temporarily turn off the Windows Firewall (you can find it in the control panel). That might make it easier to find.
If you still can’t find it, there’s not much else I can tell you that will help, besides verifying everything I’ve explained to this point. Eventually, it will show up in the Devices list, and you’ll be able to press the ADOPT button. It will take a while for it to join your network. Once it does, go back into the Settings icon (at the bottom of the Dashboard) and go through the following Menu items:
Site: Choose any site name you want (like Jenkins House), then choose your Country and the local time zone. I recommend turning on Automatically upgrade AP firmware. Leave everything else at the defaults.
Wireless Networks: If the Controller didn’t auto-detect your UAP when it first started, you’ll have to manually set up your WiFi network here. Click the CREATE NEW WIRELESS NETWORK button. Choose a name for your network to broadcast (also called the SSID). It’s OK for you to use the same network name that you were previously using on your wireless router, and as long as you also use the same security type and password in the next step, all your devices should “just work.” Or, if you want to make a separate network name, you can do that. Make sure the Enabled box is checked, choose WPA-PERSONAL for the Security, and enter a Security Key (the password people will need to join your network). Don’t check the Guest Policy box, or worry about any of the Advanced Options. Press SAVE when you’re done.
Exit back out to the Dashboard with the X in the top right corner. If you click on the link of your UAP, you’ll see its status in the right column. It might say something like “Provisioning,” which means it’s saving the stuff you just set. It might also indicate that it’s updating its firmware, since you just turned on automatic firmware updates. If that’s the case, wait a few minutes for it to finish up. When it’s showing green and “Connected,” it’s ready for you to test.
The UAP-PRO should now be showing a blue LED ring, which looks especially awesome in the dark: