First few week you will gain more from listening than talking.
Learn from the team, what are they being asked to do, what do they like, what do they dislike, what processes work, what processes don't work, are there any friction points with other teams, what is important to them, what would they like to do more of, who has the capability/will to progress....
Then build out a plan based on that information. The structure I've always used is 'Fix, Focus, Grow'.
Fix - what are your quick wins, the things that can be changed easily and quickly to bring benefit to your team and the business within the first 3 months
Focus - what are the medium term goals, these will require a little more thought, engagement from other teams but could be implemented within around 6 months
Grow - what are the bigger challenges, the ones that may need budget, approval, tech changes and so would likely be about a year in the planning.
Succession planning - you should always to aware of who in your team has the desire and the capability to develop and progress, it may not be that they could or want to be in a leadership role but they may be perfect for a different sideways role or a different upwards move into a more specialist field. This benefits you because at some point you may want to progress and having a second in command makes that easier. It also means that you are keeping your team members engaged and interested. Delegate to them (if you are unsure how to delegate look it up, there are loads of free courses online), give them opportunities to shadow you or other colleagues, consider mentor/buddy schemes, provide opportunities to gain experience that they can use in interview examples or to decide if they really like doing the role.
Praise and celebrate achievements - it can be easy to become hyper focused on negative behaviours but you need to make sure you are giving immediate praise and positive feedback when you see things being down well too.
Manage poor behaviour and underperformance - set objectives related to key activities, job descriptions, behaviour and personal development goals. Make them SMART, review them regularly and if underperforming address it immediately. Initially it should be as feedback, if the feedback doesn't produce improvement follow the formal improvement process. Be consistent and fair.