Where do I put information from a 1098 OMB?

There's not a specific Form 1098 OMB.  Form 1098 has an OMB (Office of Management and Budget) number of 1545-1380, assigned by the OMB.

To enter mortgage interest or refinancing information from Form 1098 in TurboTax Online:

1. Select Tax Home in the left pane
2. On the Hi, let's keep working on your taxes! screen, select the dropdown to the right of Deductions & Credits
3. Select Start, Pick up where you left off or Review/Edit, as appropriate
4. On the Your tax breaks page, scroll down and select the dropdown to the right of Your Home
5. Select  Start or Revisit to the right of Mortgage Interest and Refinancing (Form 1098)
6. On the  Did you pay any home loans in 2023? page, select Yes
7. Enter all relevant information on the ensuing pages

See the TurboTax Help article Can I deduct my mortgage interest? for more information.