Ethernet not working?

Hello,

Moved into an apartment, the apartment has an xfinity gateway built in already, so I got my internet through xfinity.

Now here's the problem. My internet is really spotty when I play games, so I tried to get an ethernet cable going, and there is an ethernet port in my wall. Is that supposed to connect me through ethernet, because it isn't. Is the port in the wall for something else?