I had a bad experience coming out as bisexual to my mom so I've put off exploring that part of myself for years. Now I have no idea where to start. How do you begin when you're late to the party?

There is no being "late" to the party. You come out when you're ready to come out and you incorporate aspects of your identity into your life when you're ready to do so. That can happen when you're young or when you're old and it's all fine. I'm sorry you had that experience with your mom, but I would recommend just starting where you feel most comfortable. Do you want to start coming out to more people? Do you feel the need to find LGBTQ+ groups to be a part of? Do you just want to start experimenting in the dating world? It's all up to you!

It's never too late to be who you are! If you have pushed back that part of yourself for a long time, maybe the first thing to work on is your self-confidence. Feel free to explore your feelings, to express them, to talk about it with people you trust, be it friends or anyone you imagine can be open-minded enough to accept you as you are. Maybe connecting with the LGBT community - online or, even better, in person - would help you reconnecting to that part of yourself, and feeling more confident in who you are. Remember you're not alone, and while self-confidence comes from inside, there are many people around you who can help you making it grow!