Why can't I adopt pets?

I'm all new to sims, so I watched a lot of youtube and everything to learn how to play. 
Now I would like one of my households to get a pet but I don't even have the option. Everyone says to use the phone or computer, but when I do I still can't adopt any pets. It's not a grey box or something like that because the box isn't even there. 

I don't have any mods or anything like that because I don't even know how to do that haha

Please tell me someone here knows what the problem could be.