Please I’ll be so glad if you could make my iMessage work thanks

well I can’t send message through Imesaage to any contact and I don’t know what wrong I can’t found my number or gmail or even my message turn on and I don’t know exactly what’s wrong but I’ll be so glad if you could help me with the issue I’m having with my iMessage ,I’ll be very much appreciated if you could help me with the issue I’m having right now thanks