Their are several site that can show you how to make them,
these 2 listed below are were i started.
Tutorals to get you started.
1. MS Paint
(this you will find on your computer under the Start/Programs/Accessories/Paint)
2. Paint Shop Pro
these nest two are for photoshop,
3. Potoshop #1
- this has upto 40 tips on using it
4. Photoshop #2
- this one give tuts and lessons