Day 1 at a new company is always a little awkward; especially if it's your first time. I myself usually clam up in new environments and stay really quiet (or, on occasion annoyingly loud). You're going to meet a lot of people and spend a lot of time trying to figure out how they all fit together.
One of the most important things I find myself telling students and recent graduates is: talk about your passions.
If there are aspects of your life or career that you think the people around you can help you further, tell them about it. If you're passionate about certain technologies or aspects of development talk to people about it.
If I know your name and your passions:
I can bring opportunities to you.
You're going to work with your team on a daily basis, it's important to get off on the right foot with them. Many companies care more about cultural fit than technical competency. Managers don't want to hire people that will make their existing teams miserable, no matter how smart you are. So if you've made it through the interview process, they probably thought you'd be a good fit. Don't let them down.
When I first started my current position the first thing I realized was that my team is really quiet compared to what I'm used to. I'm a super social person who loves to talk and for the most part my team isn't. If I had decided to try and change that from day one, it could've really messed things up. In an effort to provide the opportunities to socialize, I've hosted a few social events including board game lunches and other team outings.
It'll take awhile to find your place on the team and find your fit, but it will happen. Gifs of cute dogs usually are a great place to start.
If you're working at a decent size company there's a good chance you'll have someone assigned to help you get started. A lot of the time it's someone from your team but in some cases it could be someone within your organization.
If your assigned mentor is on your team: I'd recommend finding an additional mentor adjacent to your team. Sometimes issues arise and it's nice to have someone who is not directly involved with your team to talk things through.
Conversations with your mentor should be less formal but not necessarily unstructured. A lot of places have on-boarding checklists and if your company doesn't it doesn't hurt to ask for one. It's good to have a mutual understanding of the things you should be doing to get ramped up.
Honesty is also an important aspect of your relationship with your mentor. If you're struggling to find documentation or having other difficulties it's important to communicate that upstream. I don't know a single company who thinks it's perfected the on-boarding process, there's always room for improvement and that improvement relies on honest feedback.
Mentors are a great resource because they can give you the guidance that will help you be successful. Sponsors are a special type of mentor. Mentors are mostly there to answer your questions and give guidance, sponsors will do all of that and lobby for you while you're not there. They bring opportunities to you without you necessarily asking. Not every mentor is going to take it upon themselves to be a sponsor, but if you can successfully identify those people they will take you far.
Your manager is one of the few people where your success is a written part of their job description. You should have regularly scheduled meetings with your manager and it's important to utilize this time well.
If you're having concerns about joining a team and your manager doesn't know, they can't do anything about it. At the same time, if there are things you're interested and your manager doesn't know... they can't do anything about that either.
Having a good relationship with your manager will make it easier to address concerns when they arise. In previous jobs I've seen situations pop up where staff complain amongst themselves and just assume the manager ignores situations out of spite (rather than ignorance).
Be friendly and honest, and hope for the same in return.