Enable MMS messaging on an iPad

You can't if you do not have an iPhone using the same Apple ID & password.

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

Your iPad is not a cellular telephone. It has no capability to send or receive SMS or MMS messages, both of which require a cellular telephone. It only sends/receives iMessages.

You’re welcome. Enjoy your iPad.