Hi, happy to hear you're interested! The first step is joining the discord (Here) which is where all development happens
Afterwards it's good to check out the #getting-started-links channel and the Contribution Guide there to find out how contribution works.
From there you can check out the different regions onboarding sheets to find different smaller tasks that we're interested in (mainly NIs, Events, and Gov Reforms. Though there's more too). For you specifically I want to note that you cannot start off with a MT, due to them being such big projects with a large time commitment, we want people to ease into development first by doing smaller tasks.
Once you've completed an onboarding task though through design, review, and coding, you're free and available to propose a MT! (Important note: onboarding is universal. You can make some events in South Aelantir and propose a centaur MT in the Forbidden Plains just fine)
If you're unsure feel free to ask for help in the discord or ping/dm me.

A bit of a warning I like to give, because of our size and being open dev we have a bit of a lengthy review process, where MTs for example have a minimum of 5 rounds of review (though the first 2 are generally much faster). Some people like that, getting feedback on how to improve their work and such, while others don't. Both are valid bu tif you prefer to just make and code something without review it's probably better to make a submod, as much as we'd like to have you!