Changing font to Avenir


I want to use Avenir as the font for my app.

I intend to publish to Google Play and the App store.

How can I change the system font to Avenir?

(I have a Pro Account - Avenir doesn’t show up as one of the fonts in the dropdown and when I click Explore Available Fonts there’s a broken link for Avenir and poking around it seems like the cost for this is outrageous within Google Fonts for any mobile apps. I’m very confused - this is a super basic font.)

I have a .ttc font file for Avenir on my machine as well - I just want to upload and apply it.