Step 1

First you will need to use the plus button to setup where the software will scan for your iTunes library files and you will also set up an output directory here.
The software works best if you set the input directory with the format of "[music folder]\iTunes Media\Apple Music\".
This way it can copy the artist and album organisation that iTunes uses.

Step 2

This step is optional

You can click the trashcan button to remove the error logs. This is useful if you want to retry songs that have previously failed and also to clear out the database before a new scan.

Step 3

Next you can press the search button to let the software check for new songs that it hasn't converted yet, and also to check already converted songs for errors.

Step 4

Finally you can hit the play button to start processing the music. You can see information about the current session on the left, as well as an eta.
Make sure no other applications are making any noise as this will affect the sound quality of processed music.

Alternative Mode

Alternatively there is an auto-shazam mode which will process the song you are currently playing without scanning your entire library.
To use this just start playing the song you want to process then press the shazam button and the song will start processing.