You can use the steps here below to help you get to the section to enter the tax-exempt interest.
Log into your return and click orange Take me to my return button
Type 1099-INT in the Search box in top right
Select jump to 1099-INT and it will take you right to section to enter this
Select Yes on page where it asks Did you receive any interest income? Next page, choose I'll type it in myself and then put a check mark in the box labeled My form has info in more than just box 1 (this is uncommon) on the next page
If you already entered the 1099-INT, it will take you to Here's the interest we have so far screen and you just click Edit there and check the My form has info in more than just box 1 (this is uncommon) box
And Box 8 is where you will enter your Tax-exempt interest