According to
LowEnd Mac the unit supports an Airport Extreme card 802.11g. You can buy one from various places. There may be usb perifs to give you 802.11n - but g should serve fine for the present and near future. (g will handle any internet connection you throw at it)
********
BTW congrats on scoring the Mac and welcome! I loved my eMac, and it will serve you well I'm sure.