People Managers can't be expected to become experts in wellbeing - they're already tackling multi-faceted roles.
But they do need to take the lead in promoting, enlightening and empowering wellbeing issues and wellbeing practices within their teams
I won't, again, go into how inadequate a word 'wellbeing' is. Instead let's focus on what that means in practicality
1) What can you minimise? - What are the practices, tasks, events, processes (people?) that detriment the focus, productivity, stress levels, and general wellbeing of the members of your team, and how could you either remove them or at least reduce them?
2) What can you maximise? - what are the practices, tasks, events, processes (people?) that benefit the focus, productivity, stress levels and general wellbeing of the members of your team, and how could you either introduce more of them or increase them?
3) You! - what are you doing, usually inadvertently, that gives off opposite signals to what you're asking of your team? Are you encouraging them to use their leave and then not doing so yourself? Are you telling them not to work out of hours and then doing so yourself? Are you telling them to be really strict with saying no to things and then making requests of them yourself?
This needs to be collective action - they need to do it AND you do too!