I did a search but came up empty on this...

I've been thinking about buying a cheapo phone next time I'm there for my trips but remembered that I have an old EVO that I wouldn't mind using while in Negril. How do I go about getting it up and running? I'm guessing I just need to pick up a sim card and some minutes right? Can I just stop by the Lime desk at the MegaMart in MoBay and get this done?
Any suggestions would be much appreciated.
thanks