How do I add a phone number to iMessage for iPad

On your iPhone, go to Settings>Messages>Text Message Forwarding and select your iPad. Follow the prompts to set it up.

See also:

How to forward SMS/MMS text messages from your iPhone to your iPad, iPod touch or Mac - Apple Support

You have to have an iPhone number to add for that to work. See this.

Add or remove your phone number in Messages or FaceTime - Apple Support

I asked the hosts to remove your screenshot. It is showing your Apple ID email address and this is a worldwide forum. You don’t want to publicize your Apple ID to the world.

I could very well be wrong, heaven knows it won’t be the first time, but the OP made this statement which I took to mean that they don’t have an iPhone.

i dont have a phone signed in with my apple id, what can i do to add a phone number on my ipad

Demo wrote:

I could very well be wrong, heaven knows it won’t be the first time, but the OP made this statement which I took to mean that they don’t have an iPhone.

i dont have a phone signed in with my apple id, what can i do to add a phone number on my ipad

And, as I've done before on more than one occasion I misread the original post! Thanks.

Then you cannot add a phone number to iMessage on your iPad. Having an iPhone is a requirement.