Are you filing a separate return for the dependant or do you just need to add him under your profile?
If he is your dependant (you are not married or in a common-law relationship or claiming anyone else as a dependant), you can add him under the Dependant profile and indicate his income under the Deduction: Additional Dependant Information profile.
To file his income tax return, you need to create a separate return for him.
I hope this was helpful