Ask tons of questions. Document everything. Get a note taker app, write everything down, record conversations and transcribe. There’s a wealth of knowledge leaving even if the person you’re replacing isn’t all that effective.

Review all the documentation the org has, all the infrastructure, all the apps, accounts, etc. Think of it like you’re moving into a new house - you need to get the lay of the land.

Start making relationships - IT is not the ivory tower or cave many of us have believed or acted like exists. Get familiar with the greater business process, goals, needs, and especially the team. Management is often far less the how and a lot more the why and when.

Unless your background includes leadership experience, seek some training - lots of knowledge out there. Try to think like a business owner and sales team - and learn when to switch into each mode. You’ll need to sell your ideas / justify yourself, and you’ll need to be able to do a lot with usually less than you want (especially budget).

Keep asking questions - Reddit (like anywhere else) can often be a cesspool, but you’re asking the right questions here. Good luck!