anyone know how to enable imessage?

once it's on, go into Send & Receive in the same menu and make sure your phone number is ticked, not only the email address. otherwise people texting your number keep getting green bubbles. and if activation is still stuck after a day, check date and time is set to automatic. a wrong clock breaks it more often than you'd think.

settings, messages, then the imessage toggle at the top. if it's already switched on and just sits there saying waiting for activation, that's a different problem — it has to send a text message out to turn itself on, so it needs a sim with signal, wifi alone won't do it. give it a few hours before you decide it's broken.