Cannot sign-in to my apple id when I try to connect my apple id to imessages and only email shows up

My friend gave me his phone and I reset everything to put my info in it. When I connected my apple ID it was fine but when I tried to send messages within imessages or even facetime it says: cannot send Message, iMessage needs to be enabled to send this message. After looking up on google I went to settings and went to the Messages app, my email was there but the sign-in button was greyed out and there was no way to put a password. Please help.