How do I make an addendum to my taxes that are already filed because I didn’t put my student loan interest in?

[Anita01]

You would be filing an amended return.  Wait until your tax return is accepted or rejected.  If rejected just correct and refile.  If accepted follow the instructions in the link below to file an amended return.  Amended returns are filed by mail and it can take the IRS up to 16 weeks to process them.

https://ttlc.intuit.com/replies/3288565