While emulators and the Wii U store can replicate the games of the Nintendo 64, there's something to be said for the experience of holding the classic controller. Released in an age before HD, the N64 connects to televisions using the old tri-colored composite A/V cables. Connecting them is simple: match the colors to the plugs. If your TV doesn't feature composite connectors, you'll need a go-between to make the connection.
Intermediate Devices
There are a lot of devices already part of most entertainment systems that can function as a go-between for your N64. Blu-ray players, DVD players and A/V receivers all often feature composite connectors, and in the case of some newer equipment, connectors for high-definition equipment as well. By using these machines as a go-between, you should still be able to enjoy your N64 on your TV, even if the TV itself doesn't have composite connectors.
Converters and Adapters
If you don't have any other devices that can bridge the gap, you'll need an adapter or converter to connect your N64 to your TV. Before purchasing an adapter or converter, you need to look at your TV's connectors and find out what it can handle. Once you've determined what other connectors it has, like component or HDMI, you can track down an adapter or converter made to connect it with composite.