How to activate my iPad 3rd gen?

Ive had this for a couple of years its 3rd generation but about a year ago i restarted it to change the apple id cause it would nt let me sign out unless i put in the apple id password which i forgot. Since then it says “your ipad cannot be activated because the activation server cannot be reached. Try connecting your ipad to itunes to activate it, or try again in a couple if minutes.” Idk what to do to activate it.

[Re-Titled by Moderator]