Open the profile of the person you want to add to your friends list and click on "Add to my friends". It is a red button on right hand side of the screen.
Where do I find my friends on my profile?
You can find your friends by clicking into "my profile" and going to the section "social"
On this same page, you can find the button "refer your friends" which directs you to the page with the link to send to friends you would like to join GuesttoGuest, and earn some GuestPoints.
You can also remove a friend by placing your mouse over their picture and clicking on the delete button, as shown below: