Hey Dan,
Linking a credit card or bank account to Paypal is one way, but another very easy way is to just buy an EBAY gift card. They come in various denominations. I have bought 25's and 50's in the past. My wife has also given them to me on special occassions. I know for sure that they have them at KMart and Kroger. I'm not sure where else to get them.

Don