There are two ways to add folio numbers:
1. If it's a new mutual fund investment. On the buy form in the mutual fund category, on bottom of the page, select the box for 'Click to Enter Additional data for selected Mutual Fund'. Once this box is selected, you can enter details like Folio Number, Lock-in Period and also you can change the Agent, if required.
2. An already entered mutual fund. On the summary screen right click on the mutual fund name and select "Edit Selected Asset". There you can add the folio number.