Originally Posted by dimsumsauce

Your digital/paper boarding pass will show the TSA Precheck symbol. I don't recall being able to add your loyalty number on the check in page. I found that it had to be done at the check in desk.

Originally Posted by Jebby_ca

TSA Precheck should show up on your boarding pass once you have entered your KTN, and the details of your reservation match with your TSA Precheck information.

You should also be able to update your FFN during OLCI as well. If not, you'll have to do it at the airport.