Open a building. For more information on how to do so, see section 4.6.1., 5.4.3. or 6.1.1.
Go to the building card (see image below).
Click the icon "Comments" (see the first image below). When you do so, a comments window 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 with the text you entered in the field "New comment" will be added to the building you are working with (see the second image below).
