To register E-Mandate, first, click on the URL that you received in your email from BSE StAR MF. You will land on a new page wherein; you need to login. If you login using another email address, then you will get a One Time Security Code which needs to be entered here. In the next step, you will find the automated page that includes all the details where you just need to add your Mobile Number and Aadhaar Number and click on eSign Now. Then in a new page, enter your Aadhaar number and generate OTP which needs to be entered. Once you enter the OTP and click on Submit, the E-Mandate gets registered.
For complete details, read here: https://www.fincash.com/l/guide/register-emandate-mutual-fund