[Feature request] Finalise and complete the Users' Guide

[thatfloflo]

Describe the solution you'd like
Add a documentation section with information for app users, running from installation to practical use and data extraction to (basic) troubleshooting.

[dakrismeno]

as a specific request for @cwyc8 : we need to add the "remove underscore" instruction for generic versions in the user guide (I will explain details next time you're in). Thanks

[dakrismeno]

Request for @cwyc8 : add a short section on the memory game (I have screenshots ready, please remind me).