Depends on what you are wanting to install it on. As for the API need, not really sure what you are meaning with that so I for installing Mailman 3 similar to what you see here with Postorious and Hyperkitty, I would recommend some great instructions I could find by Kelly Close who often posts on here. They are at this link:
https://docs.google.com/document/d/1xIcSsoNFp2nHi7r4eQys00s9a0k2sHhu1V5Plant...
They worked great when I was installing for a ubuntu 18.04 set up. However I needed to install on 20.04 and that required a few deviations and was a complicated install, so if you can do 18.04 I highly recommend the link above. (Kelly, if you read this, thank you for making those instructions, they saved me when beginning my set up)
Note: Using instructions and not installing from source means that a lot of people can't help you with problems you come across during install. I found people still try to help but it's much harder. I will link the options from the Mailman website, however I found them difficult to follow when I was trying. https://docs.mailman3.org/en/latest/install/install.html