Login to your Gmail account.
Once the page has fully loaded, look on teh left side of the page.
You’d see a sidebar.
In the lower part of the sidebar, is an input box that says: “Search Chat and sms.”

In that type the number, and ENTER. A box will pop up. Name your contact and select its country.
THATS IT.
Now u can chat with him normally
NOTE THAT SMS REQUIRES CREDIT. U ONLY HAVE 50. AFTER THAT U’L HAVE TO BUY SOME MORE!