From this page, you can perform a search in order to find a user, whatever is his status (subscribed, unsubscribed, pending). The search menu allows you to find an email address or a mobile phone number.
Once you have found it, click the button "Actions" to see the details (i.e. user status):
Clicking on "Edit" leads you to a page when you can update every user data available:
The tab "Recipient fields" contains all the user's personal data:
The tab "Set recipient status" allows to change user status using the dropdown menu and then clicking on "Save" (e.g. from subscribed to unsubscribed):
The last tab, "Assign recipients to groups", shows the groups the user currently belongs to, and you can simply add or change them by checking the group name and clicking "Save":
Besides recipient details, you can here view user behavior as well: statistics referred to that specific user and his click details. Just select the corresponding feature to view the data.