In an ideal world, first thing I would do, would be to get agreement to clear my calendar for atleast the first week or two, so I could mentor and coach the real basics. But we have so many resources available to us nowadays that I would do a few things:
As part of their onboarding, would get them a months MoT Pro membership to get them started (if we don’t already have licenses).
Build a list of courses/talks etc which I would recommend them completing as a basic need
Spend time each day walking them through basic testing concepts, team processes, the product and also introducing them to key people for them to get to know and work with
Assign them a buddy alongside me who is a peer who can talk to them and work with them without the manager-employee barrier being in the way and allow them to shadow them working as part of the team, eventually allowing them to pick up tasks along the way
Celebrate every success with them as they complete and grasp a new concept, giving them opportunities to then apply them and sharing with the wider teams
I’d want to ensure they build up a passion for what they are doing and feel like they are part of the team on the same journey as the rest.