There are two ways to add a mortgage to an existing own property.
Option 1: From the credit report
Pull a credit report and select to import the liabilities. You can choose which liabilities to import.
If you have already pulled the credit report, you can click on the Import button on the Liabilities section and select the mortgage you need.
To link the mortgage to the property:
A) Go back to the property on the Owned Properties section and edit the details
or
B) On the Liabilities section, click on the pencil icon on the desired mortgage and select Add Collateral
Option 2: Creating the mortgage manually
On the Credit & Liabilities page, go to the Liabilities section and click on Add Liability.
Select Mortgage from the dropdown menu.
Click on the pencil icon to add details of the mortgage and/or link it to a property.