Can you get WiFi on a eMac?

You can buy external Wi-Fi cards, and some plug into the USB port directly or via cable. Try this search result to get ideas.

Side note… I’d recommend picking up a USB hub to plug into your eMac. There are only three ports, so you’ll need some extra real estate if you are going to have things plugged in permanently (i.e. the wifi adapter, the keyboard, etc)

The emac has a slot for a internal AirPort card. You can get one here.

A “new eMac”? They haven’t been made for a few years, so either it’s not new or not an eMac.

They do have AirPort card slots, but you’ll need a specific card for many of them that is not the same as the card sold today and may be hard to find. If you pull out the cover of the CD-ROM, there is model info on a silver sticker. If you give us that info I can tell you which AirPort card you need.