how do I add phone # to receive messages on ipad? Currently only have email address listed and want to add phone # .

Use the same Apple ID for iMessage that you are using on your phone. If you are, go to Settings>Messages>Send & Receive, tap the ID, sign out, then sign back in again.

You can't manually add a phone number. Your iPhone number is automatically added when you enable iMessage if you are signed into the same ID in Settings>Messages>Send & Receive on your iPad as you are on your iPhone. (If you don't have an iPhone no number will be added.)