can I enter tuition credits later? as my child has not filed a return yet

[TurboTaxSusan]

Yes, you can.

Please see these TurboTax Canada FAQ for more info on how to transfer tuition in TurboTax: 

How do I claim my tuition fees?
How do I transfer my unused tuition credits to someone else?

How do I enter tuition transferred from my spouse/partner or child

How much of my child's or spouse's unused tuition credits can be transferred to me?