There's quite a few steps for this. There is a massive amount of work. As Wikipedia says
"literacy in Chakma script is low," so who would you be doing this for?
There is currently no locale for the Chakma language so first a new locale for that needs to be created and added to be supported by the system software. As Linux Mint is based on Ubuntu that needs to be done at Ubuntu side. Ubuntu have specific steps and requirements for this, which I'll get to. On the Linux Mint translation pages on launchpad you can help with translation of Cinnamon software and the Linux Mint tools (Software Manager, Update Manager, and so on). Most other software is translated at Ubuntu side but a lot is also done by the developers of that software themselves (like MATE, KDE, and Xfce; you'd have to work with those projects directly to add support for your language and translate it there). Even then, support for a new language won't be on Linux Mint till the next major Linux Mint release—which is Linux Mint 19 in 2 years time.
So you have 2 years to get it all done (which isn't enough time so ideally you'd find other native Chakma speakers that also speak English and form a new translation team).
Ubuntu have a guide for new translation teams that also covers how to add a new locale (see section at the end): https://wiki.ubuntu.com/Translations/Kn ... artingTeam
. Once all those steps are done we can also add Chakma to the Linux Mint translation pages.
Somebody else asked about translating for a fantasy language and was given information on how to do translations on his own system only, without as per above making it available for to users. Perhaps that is a better fit for your intended use (you could copy such translations to other users their systems manually). See here: viewtopic.php?f=90&t=224090