BSE has not given us the option to send Mandate details in the Purchase order request. However, there is another way that you can Purchase through Mandate.

To Purchase via Mandate, choose "Send Payment Link on Mail" option while placing the Purchase order and Submit.

Then Go to Profile list menu in your Advisor login. Search for the client and Click on "Go To Cart" from the actions on the Right.

This will open the BSE Cart where you will be able to choose Mandate and confirm the order.