You’ll want to use the “new” API connector. It has some updates that make it both more powerful and also a bit easier to use (but still not easy).
I’m not the best person to advise you on how to format the POST, but here’s some of the basics. Arrays are supported. You’ll set up the POST in the API connector with static (i.e., not dynamic data). Then you’ll confirm that works and establish a connection (using a button at the bottom called “initiate” or “connect” or something else worded like that I believe). Once the connection is established, then you can use workflows within the API section to overwrite the static values with dynamic ones.
I wish I could explain it better but it’s been a while since I used the APIs and forget much of the details. In my experience, this is by far the most difficult and confusing part of Bubble. There’s a fair amount of answers on the forum so definitely read through those. And, if that doesn’t work, you may be able to find someone who knows this stuff well to create an example if the Forum App since a lot of people would benefit from being able to see a working example.