Ok. Once you have your 4 images you need to open up your paintprogram or photo editing software.
My actual software isn't photoshop however most of todays photo editing software packages offer similar styled options anyways.
I'll try and show the development in screen prints so it's easier to understand the creation process.
First Open up your program and select new image. If it depicts a size thats too big from the start go to edit image size and resize it to whatever your comfortable with.
Once you have done this your new piece of paper or working canvas will appear.
Okay This is where the fun begins. Think of a decent background colour. In this one will go for a good standard GIJOE Military Green click on Flood Fill Tool and drop your colour onto the page like so.