Aeneas is a tool used by Scripture App Builder to synchronize text with audio. It is able to analyze an audio file and compare it with the words of the text, to produce (in many cases quite accurately) timing files to enable highlighting of words in the text when those words are being said on the audio.
If you use HearThis to record text verse by verse following your Paratext project, the timing files are created automatically. But if your audio has already been recorded, Aeneas may be a good choice for rapidly producing timing information.
Installing Aeneas is a separate operation from installing Scripture app builder and it is a rather complicated process. A step by step process how to install Aeneas and the different things it needs to work is described in this document (also available from the Scripture App Builder help menu, look for 5 - using aeneas for Audio-Text synchronization.
The document describes downloading Python 2.7 from the Miniconda page. If you have Paratext, you might be aware that Paratext installs the Python language on your computer so you might wonder if you need this. Go ahead and download Python 2.7, because the version Paratext installs is 2.4, not good enough for Aeneas.
Another potential confusion is the version number when you are installing Python. The instructions tell you to download the package with Python 2.7, not Python 3.5. You may have clicked on the link for 2.7, but then wonder if you got the right file if you see an install screen like this (with 3 as the version number).
Don't panic, the Miniconda tool that installs Python 2.7 has its own version number. In this case, Miniconda version 3.18 is ready to install Python 2.7. The install instruction document describes how to verify your Python version after install.
Important detail about audio files
To use Aeneas, you need to have separate audio files for each chapter of your text, even if you have the whole book in one file as is standard with Paratext. If your audio files were made by Faith comes by Hearing, they probably already come this way, one chapter per file. If the audio files are not one file per chapter, Aeneas will fail totally to synchronize. If your audio file has more than one chapter in it, use an audio editing file like Audacity to split it up into individual chapter files.