How do i add a site to GA

Find the menu

You will see a menu on the left. At the bottom, find this gear icon and go up and press create

Then you will need to type a bunch of names, for your account, property, etc. Set the checkboxes at your own liking. P.S You will not create a new GA account by clicking on that. It is something different. I think of it like having multiple domains (Accounts) and subdomains that you want to track (Properties).