I need to go back and fix some things and it’s not letting me. what do I do?

Have you already filed your return and has it been accepted? If so, you can't make any changes to your original return. You must prepare, print, sign and mail an amended return form 1040X to make changes.  This form will be available later in February.

DO NOT change your original return until you start the amended return. Here is a link to help you amend a return if that's what you need to do: https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed

If you have not yet filed your return, can you see major headings at the top of the screen such as Wages and Income (or Federal Taxes), Deductions and Credits, etc. You should be able to click on them to access what you want.