No worries. Questions is why we're here.
I've built two so far and both were 120" 16x9 screens.
I got my spandex from spandexworld. Good quality stuff is important.
This line is what's recommended for AT screen use. Color depends on what type of screen you may need. Specifically the moleskin matte is what you want to get.
https://spandexworld.com/c3/catalog/product/6409
Stretching is a pain. There is a product called screen tight that is used for stretching cloth outdoor screens for windows/porches and such, but it supposedly works great for this too. Would recommend.
Buy a good staple gun and go slow and be patient if you don't go the screen tight route. Don't want to over/under stretch. Everything HAS to be uniform.
Building a frame is easy. Get the straightest poplar or any other wood that will hold it's shape well and use pocket holes if you can. If not, use corner brackets of some sort meant for frames.
My speakers are behind my screen, but are in-wall so I opted for a french cleat when hanging it. If you are doing cabinet speakers, that probably won't work for you.