How to Unsubscribe/Subscribe a user

You can do that from the user's profile. From either your Contacts tab or the "Lists & Subscribers" page under your Email & Marketing tab, you can search or "filter" to find the name of the person you are looking for.

Once you find them, click on their name to get to their profile page.

In the upper right-hand corner, you will find the toggle button to Unsubscribe or Subscribe that person to your email list.

You can also subscribe users in bulk from your current Contacts tab by marking them and clicking on More. Then select Add Contacts To List and select to which list you want to add them. This will subscribe and add the contacts to the selected list.