How to I set my number to "Do Not Disturb" (DND) so that all calls go direct to my 2ndNumber voicemail?

You can toggle Do No Disturb (DND) on/off by dialling:

*76

From the WebPhone or app. So firstly, log into your 2ndNumber dashboard, or start the app. Then once you're in simply dial *76. The voice prompt will tell you if you are now activated or deactivated.

When activated, all calls will go direct to your voicemail on 2ndNumber.