Easy! If you're logged in, head to My Balance > Verify To Withdraw > Enter your mobile number, get an OTP and you're all set. 😀
If you're logged out:
1️⃣ Log in with your registered email ID and password
2️⃣ Enter your mobile number, get an OTP, and that's it.
PS: Make sure the mobile number you wish to verify is not registered on any other Dream11 account.