7-11
Walgreens
CVS
Walmart
Food 4 Less
Target
K mart
Tmobile
AT&T

And many many more places.

Doesn't seem to hard but it depends I guess on how savvy you are with your fingers.

Most you dial the 1-800 number, or you can even now go to a website.  Enter the serial number, some require a name and address, (use spoof info if you want) enter a password, charge phone, add minutes and you're set!