Using external modules

Hello Mastodon team,
It’s a pleasure to use Mastodon built and maintained by you guys.
I am very new to having my own instance with mastodon. I want to add personalized features to the Mastodon instance, Like using npm libraries like axios or using yandex translator or similar ones and then reflecting back to the user accounts, Can you please guide me where to start to learn how to install such packages and use them in my instance for users.