In the “Contacts” section, press on the icon “Add” and enter an ID (7XXXXXXXXXX).
You can also ask another user to send you the details of the contact you wish to add.
In the chat, press the “Attach” icon and select “Share contact”. Select a user and share his/her contact information.
Select a user in the “Contacts” section, and press in the menu.
Select a user in the “Contacts” section. Under “Chats in common”, you’ll see which chats you are both included in.
Select a user in the “Contacts” section, and press “Delete contact” in the menu.