According to the Help it should be
"
Sign in to My Virgin Media
a. Go to Account settings, then Account details
b. Tap Manage next to Manage your Virgin Media Mail app password under Virgin Media Mail
c. Then, under Virgin Media Mail app password tap Generate new App password and follow the instructions
"
I don't have the Virgin Media Mail option in my Account settings
Hi nialled
Welcome back to the community forums
Sorry to hear you're having issues with generating an app password
The Virgin Media Mail tile will be on the Account settings page rather than the Account details page as shown in the image below. Once on the Virgin Media Mail Settings page, scroll down to the App Password section and click the Generate New App Password button. 
I don't have it
Hi nialled,
Thanks for taking the time to contact us via the Community. It's lovely having you on board with us in the Forums. ⭐
I can see you're already in a private conversation with my colleague who has been helping you to resolve this.
We'll leave this with them to avoid multiple agents working on the same thing 🙂
Thanks,
