The contacts page is where you can see all of your friends on immi. Clicking on a friend name will open their contact page. In the contact page, you can change the name they show up as on your account, see all updates they shared with you, or remove/block them should the need arise. If you want more common updates from this contact, you can click the bell in the top corner to enable notifications when that user shares an update.
To add a friend, click on the button in the top corner. To add someone already on immi, search for them in the search bar; to add someone who isn't on immi, click the invite to immi button and you will copy a link that you can share on any platform you like.