Fiber Ethernet Ports

Good morning, I hope you have a few seconds to help me with this issue. .  I moved into an apt and have AtandT fiber. I was hoping to plug in an ethernet cord into it as I used to with my comcast modem, however I couldn't find the modem. I found it in the back of my closet finally, it had been secured in. I was wandering if I needed a long ethernet cord to stretch to my playstation from the closet. Then someone mentioned I could use the ethernet slots in my walls around the apt that I thought were phone jacks. Is this true, and would I simply need to just plug in a ethernet cord to them or do I need to do something else.  Any help would be great, thanks!