How do I change my iMessages so they are sent from my cell phone number instead of my email?

I have looked at at least 10 different Apple Support Questions with close to the same question as me but they all give the same answer, go to Settings > Messages > Send & Receive and then i will be able to click the checkmark on my phone number instead of my email. Theres only one problem, my phone number isn't an option! It says my email and that is it. How can i change this so that i send iMessages from my phone number instead of my email?

All it says on the Send & Receive part is Apple ID: (my email) and then underneath it is YOU CAN BE REACHED BY IMESSAGE AT with again my email this time with a check on the left hand side at the beginning of my email and the i with the circle around it on the right hand side of my email. Underneath it says Add Another Email but it will not let me put my phone number instead of an email. I have also tried clicking the i but all that does it bring me to another page where it asks if i would like to remove this email.