You should not amend your state return to add and file your M1PR. This is a separate form that needs to be printed and mailed.

To get back into your return after filing please take the steps below.

1. Login to your TurboTax account.
2. In the Welcome Home box, click Visit My Tax Timeline at the bottom.
3. In the SOME THINGS YOU CAN DO section, click Add a state.
4. Click on the State Taxes tab.
5. Click Edit next to your Minnesota return
6. Continue through the return. CRP instructions below.

Certificate of Rent Paid (CRP) is at the very end of the state return, after the questions about penalties, extensions, etc.  Look for a page titled "Other Forms You May Need".  Check the first box, Property Tax Refund (Form M1PR). (screenshot attached)  That will take you through the section for the renter's credit. 

To print your M1PR go to My Account > Print Center.

You may also find the following FAQ article helpful. https://ttlc.intuit.com/replies/3300669