Open a lease. For more information on how to do so, see section 4.6. or 6.1.
Go to the lease card (see image below).
Click the icon "Comments" (see the first image below). When you do so, a comments window specific to the lease you are working with will open (see the second image below).
Go to the comments window.
Write something in the field "New comment" (see image below).
Click "Send" (see the first image below). When you do so, a comment will be added to the lease you are working with (see the second image below).