And your question is..?

how do I add another T4 form into my file? There is no any option to add more T4s. Help me please.
Thank you.

how do I T1 adjustment

Wait until your return has been assessed.
Then you can submit form T1-Adj. Request for Adjustment, which. Is downloadable in fillable format from CRA. Attach any relevant slips or receipts.
Another option exists if you have My Account. You can make changes to your return on-line.
After considering the Request, CRA will send you a Notice of Reassessment.

@Jamesboisse Can you provide more details about your problem?

If you need to add another T4 to you file, you can do as IntuitJacquelyn suggested above. You can also click on the “Find” icon in the top right and search for “T4”. Select “T4” from the list and then click the “Go” button. Then click on the Add T4 for [Your Name] button.