So this is the first time I've installed a stock so could use some help.

The UBR just comes with the buffer tube and I've completed a build using a stripped lower.  All I need to do is put on the stock.

However, I dont have the Buffer Spring and was wondering what other parts I will need.  I have the tools to do this.  Any advice would be appreciated.

Thanks!

Just need a buffer and buffter spring.  However, I would hold off on installing the stock if you haven't installed the LPK in your lower yet.  There is a spring+detent for the rear takedown pin that needs to be put in before the stock.

Buffer.  Buffer spring.

Flathead screwdriver.    Blue Loctite is also highly recommended

ETA:: And yes, you'll want the rear receiver pin, spring and detent, as well as buffer detent and spring with it.
Install the buffer detent and spring along with the included receiver extension, then do the rear receiver pin when you affix the top stock body.

Thanks fellas.

The lower is all put together and good to go.  I do have one more question...

When I screwed it on to take a look how it feels, I noticed the lower half of the stock will not allow it to screw tightly in.  Is there another part that I need to buy as well?

Looking at the last AR I purchased there is a threaded extension, so it appears.

Not really sure what you mean, could you provide pics?

Just installed my 1st UBR.  

What did you screw on?  There should be two things that screw in on the UBR install.

1.  The buffer tube (entry receiver extension) should screw into the Lower receiver.
2.  the screw that tightens the cheek piece (Main Tube assembly)gainst the lower receiver, trapping the detent pin and spring.  

This is the only tightening or screwing that should be done in the assembly process.

Did you separate the stock body (lower half of the stock) from the Main Tube assembly before putting the main tube assebly on the buffer tube?

wow, ok.

So my noob ass was putting the stock on with the buffer tube already screwed in inside of it.  Thus, when I would go to thread the stock there wouldn't be a tight fit.

I popped the buffer tube out and put it on the lower and then threaded the stock in.  Haha, worked out fine.

With that said, I still need to pick up a buffer spring and buffer.  What are the top of the line ones? This is going in my best AR.

Enidine!

ETA:  FTW!