We're fortunate enough to have lots of them here in Arizona. If your radio can send DTMF tones (telephone tones) you can use your radio with a repeater that supports autopatch. There are ways around this, so if you don't have a radio like that let me know and we'll come up with other options.
First thing to do is find a repeater that does! Hopefully you know how to look up the repeaters for your area, if you don't let me know and I'll try to help. Find one that supports autopatch and make sure it's public (not all are). Dial up that repeater and make sure you can hit it. You can sometimes ask for help if it's a busy repeater and peopel will be more than happy to help you.
Most autopatches work like this, but not all! Say your call sign and that you intend on accessing the autopatch. Without stopping your tranmission dial *+the phone number and end your tramission. The repeater should let you know that you've accessed the autopatch and it will connect you. Talk to the person on the phone like you would any other person on the repeater. When you're done, say your callsign (helps to thank the repeater owner for use) and press #. # ends the call.
That's it! Not terribly difficult. Goodluck!