Often, these are the easiest traits to come up with. We enjoy the characters we see ourselves in and we relate to those better - and it feels good to relate to characters who have good traits! Our suggestion is to pick one primary virtue as a launching point for how you're going to shape your character's personality. That doesn't mean it's going to be their only virtue or even their most impactful one, necessarily, but think of it as the thing that sticks out most about them in a good way.
If you were introducing your character to a friend who's never met them, how would you sell them? This is a fun way for me to pick a virtue, mostly because I get distracted thinking about trying to help my original characters make friends like a mom at the park.
This is covered a little more on the flaws page, but remember that every part of your character will influence their personality, so don't be afraid to base their flaws off their virtues or vice versa. Unless you're aiming to have a completely unlikable character, chances are they're going to have some traits that are at least a little virtuous - and if you ask us, the very best villains are compelling characters because of the fact that they're not pure evil for the sake of evil.