To enter a space
Move the r mark over the INS, then push the MENU knob. The space is entered in the position under the ? mark on the character entry row.
When there is a character under the ? mark, the space is entered in that position, and that and subsequent characters move to the right one at a time.
4
Move the r mark over
INS.
Push the MENU knob.
Space 
Move the r mark over RET, then push the MENU knob. The ? mark over the space on the character entry row changes to a r mark.