Q: Imessage on Macbook wont link to phone #

After regrettably updating my macbook pro to el capitan which made my life increasingly difficult I have now noticed another just wonderful perk to the update (besides having to transfer all of my iphotos to photo and my gmail account not being able to be linked to my mail now) my imessage wont link to my phone number like it used to so I could "text" people from my computer. Any suggestions would be lovely for this imessage issue along with if theres a way to revert back to older software. Thanks guys!