Can someone please tell me exactly how do I create a banner. (As in full details)

I'm not sure what details tu want, but I'll try.
It's probably easiest to make it on photoshop, just start with a new layer, make sure it's 800x100, & then copy/paste pictures on it.
Sometimes it's easier to take a huge screencaps & cut it down to size.
Uhmm, I normally blend pictures, which tu have to erase parts, and such, then editar the colors...
Idk, if tu are familiar with photoshop it's pretty easy.