How Do I Block or Unblock Someone in the Chat/IM?

To Place a Block

First, ensure you have the initial IM window open by selecting the Chat icon at the bottom right of the page. 

To block someone you no longer wish to chat to, select the '⌄' symbol next to their username. From the drop-down, select 'Block User'.

To Unblock 

Select the IM icon to display the initial chat window. 

Select the three dots '...' at the top right corner of the Chat window. From the pop-up menu select 'Manage Block List'. Select the username from the drop-down then  'Unblock'.