First, create an Offset Savings Account using the plus button on the dashboard.
Complete the Basic details of the Savings Account confirming the owner of the account, give the account a name and add the balance. Check the fee rate and interest rate (these pull through from your Plan Settings) and update if necessary, then click Done.
Note if the Mortgage is Jointly owned, then the Savings account needs to be in Joint names otherwise it will not be visible in the drop down window shown below.
Next, add the Mortgage using the Debts & Loans section found under the plus button. Select Debt and enter the details of the Mortgage. At the bottom of the screen you have the option to select the Savings Account to offset against this Mortgage, then click Done.
You will then see the Mortgage details in the Debts tab of Year View:
If you had already entered an existing (conventional) Mortgage and have switched this to an Offset Mortgage, you will probably have noticed a slight reduction in the number of years it take to payoff the Mortgage. This is because the linked Savings Account is now being offset against the outstanding balance of the mortgage.
You can see this using the Debts chart.