Packet radio requires a TNC (Terminal Node Controller) like this Kantronics KPC3+:
This goes between your computer and the radio, much like a modem.
What are you looking to do with packet? Depending on your goals, other technology may be more appropriate. For example, as hams we can run high power ( I believe up to 200 watts) on standard WiFi 802.11 frequencies. This means we can have a wireless network that our neighbors would only dream of! (of course all Amateur Radio rules apply)
Packet radio on 2 meter isn't going to give you any high-speed connectivity, it's more about sending text messages and the like.
Depending on what you want to accomplish, there are technologies to explore.
You may want to check out TAPR
http://tapr.org/organization.html
-Mike