Make sure that you're in Direct Mode when you save.
Code to save:
SAVE "TITLE"
If you're code isn't in Slot 0 you need to do it differently:
SAVE "PRG2:TITLE"
This will save the code in Slot 2, and call it Title.
Change the number to match the correct slot. PRG is only necessary if you want to save something that isn't in Slot 0.