What you need to install "for TTS" is a voice provider, which you most likely already have - AOSP includes Pico TTS and even the smallest Gapps include Google TTS since marshmallow...
...but then you need a software that actually knows how to pass text to the TTS, for example most maps apps can do it, but for general purpose copy-paste-and-listen you'll want something like this:
https://play.google.com/store/apps/details?id=com.hyperionics.avar&hl=en (first one I've found, no personal experience) or alternatively using a screen reader like Talkback (and learning the annoying controls they use - did I mention poorly designed apps don't work with them anyway?)