Where do I enter boxes 42 and 105 on a T4A slip?

If you click on the Income tab>T-slips> T4A> you should find both box 42 and box 105 in the first entry screen.

Box 42  RESP educational assistance

Box 105 scholarships - eligible for full-time.

Turbotax won't recognise and entry in box 105  of the T4A

@heathermuirhead, in EasyStep or the Online interview, you should see it about halfway down the T4A entry page.
In the T4A entry window in desktop Forms view, click the entry field in the bottom row to enter an amount from Box 105.

If the software is not letting you enter an amount, please reply with more detail about any error message you are getting.