To choose a letter, move the cursor over it and pause. If you keep moving across a letter and on to another, it will not be chosen. When a letter is chosen it is added to the 'Message Area' at the top.
Choosing Faster or Slower near the top of the window will alter how long you need to pause before a selection will happen.
To choose a letter twice in a row (such as the two T's in letter) choose 'T' once and then move OFF the 'T' and back ONTO it.
Deletion of the last letter is done with Del. DelWord at the top will delete the previous word. Clear will clear the entire message area. If you remain on the Del or DelWord the deletion will be repeated.
If you choose Cmd at the bottom right another window will pop up with many commands to choose. One of them is Quit - to exit Sue Center. Another is Help - for complete documentation on all aspects of Sue Center. In these help pages the sequence Cmd > Quit means to choose Cmd and then choose Quit.
To the left of the letter area is the 'Word List' and the 'Short Words'. Read about both of these in the 'Word List' help topic.
If you choose Suspend at the bottom it will change to Resume. At this point the entire main window will be suspended and will be INACTIVE until you choose Resume to activate it again. This is used for when you wish to rest and ponder without choosing anything inadvertently.
Normally letters are entered in UPPER case. You can choose the SHIFT command at the right hand side to toggle to Shift or mixed case. The first letter after this choice will be in Upper case and the rest will be in lower case. Choose it again to enter a capital letter. Choose it twice in a row to return to UPPER case. This behavior may seem odd but it works well.