Set the setuid bit on the executable

.. code-block:: bash

  $ sudo chmod u+s /usr/bin/screen
  $ ls -l /usr/bin/screen
  -rwsr-xr-x 1 root screen 360952 Jan 18 2038 /usr/bin/screen

Update your .screenrc

.. code-block:: text

  multiuser on
  acladd bgates,lellison,gvanrossum,dknuth,dnorman

User 1 starts a screen session

.. code-block:: bash

  user1@localhost $ screen

User 2 connects to the screen

.. code-block:: bash

  user1@localhost $ screen -r user1/