Decals and pilot Figure
Each pdf file has the basic insignia for decorating a model. Get some full sheet label paper from the office supply store and print with a color printer.
Printing - when you download the decals they will appear as a single page on your browser window. Save them to your computer as a pdf. Select print and then click on "copies and pages" look at the menu for "page scaling" and select "tile pages". The default may be to fit to one page and that will make the decals 1/2 size.
Once you get them printed, cut them out and apply.
The pilot figure can be folded around foamboard, glued with a smear of white glue and cut out. Alternatively use cardstock. You can shade the pilot figure over the black and white with color pencils or pens.
It's fun to search imagery for your model and use some of the distinctive markings and squadron numbers. Get creative with color markers, pencil for panel lines, and odds and ends for machine guns, aerials etc... keep the model as light as possible.