SO I think I have a decent build that I would like to enter into the Modern Musket contest. I have generated a URL, pasted it into entry form, and have everything laid out ready to submit but it says choose file and I don't know of any file I can choose. This may be because in order to choose file, I need to save it. Well, I log in and load in my build using the URL and try to save, but it pops up saying I need to be logged into my AR15.com account to access save features. But I am logged in!!! If possible, please help. Thanks!

That's not what you need to save. If you have the URL you need to put that in. Load Gunstruction using that uRL and you will get back to your completed rifle. Then choose the 'Photo' mode. You want to make a picture of it and THAT is the file you want to upload. So, position the rifle how you want it in the picture, choose background, lighting and so on. Then, take a screen snapshot. That will open in your web browser. Right click on the image (if using a PC) and select 'Save As' and give it a name and a place to save it. The picture will be saved in a .png format. Then, select that file to upload. Presto - you have the picture of your rifle uploaded :)