I still use one from the old days every once in a while myself. I don't know what you need to know, just load the tape in it, turn the wheel until you get the letter you want and squeeze. Repeat as necessary. Cut the tape with the built in cutter, remove the backing tape, and stick the label where you want it.
Works good, lasts a long time unless it gets hot, then it will go blank.
Lewis
P. S. It will look better if you trim the sharp corners a little bit with sisscors.
LL