In order to have the 1040 x show you have to have started an amended return. To do that you do not open your regular return, but you have to go a little lower on the page that opens Turbo Tax and click on the Need to Amend a Filed Return? Then chose your original return and follow the instructions. Once you have started your amended return, then the 1040x is way down the list of forms, before the Estimated Tax forms.
If you haven't filed your return, then you don't have to amend it at all. You just have to change some of your entries on your original return.
But... I imagine your problem is that beginning last year, most filers will not receive the complete amount of their mortgage interest paid on their primary residence as a deduction on Schedule A. That is because the amount in Schedule A for Taxes You Paid (State income and state and local property tax) and the amount for Interest You Paid are entered in the form, but the total allowed is $5000 if you are filing single and $10000 if you are filing joint. The amounts are probably treated differently for your state taxes, so you should enter them, but amounts on entered above that $5000 or $10000 threshold have no impact on your Federal bottom line.
