Adding the alternative/addon reading software is not that hard.
Here is a guide. With the Aura One, you need one of the
latest releases of KOReader.
Once you have the loading program installed, (the guide covers using Tshering's "Kobo Start Menu") you just place the program folders, from the download packages into the .adds folder that the KSM install creates. Then all you do for updating to a newer release is copy/merge the new folder over the old one in the .adds folder on your device.
Luck;
Ken