I do mine like this:
Go to Paint. Paste the first picture in. Go to Image -> Stretch/Skew and put in about 30% for both Horizontal & Vertical (you can go back and adjust the size if you want). Repeat for the second picture & drag it to the right of pic 1. Add whatever text you want (dates, etc) & Voila! That's it. Some people make theirs more fancy, but I don't have the inclination for all that.