Open a Guitar Pro file, or a PDF with standard notation and tab, exported from Guitar Pro or from notation programs like Encore (the app reads the notes and rhythm from the notation; hammer-ons, slides and bends are not read from PDFs yet).
Press Start listening, choose your interface, then press Play. A note counts when you pluck it (the app detects the pick attack, or a pitch jump for hammer-ons and pull-offs) within 150 ms of the beat, and shows how early (−) or late (+) you were. Chords and power chords count when the notes of the chord are sounding (for big chords, most of them).
Run the Latency test in Setup to measure your delay, or nudge the offset yourself. After a run, a button in Session can shift the offset by your average. Use headphones so the click doesn’t leak into your input.
Right-click a bar (on the tab or the timeline) to start playback there, and right-click it again to start from the top. The rewind button left of Play also goes back to bar 1. Loops ignore the start point.
Loop a bar by clicking it. Speed up raises the tempo after every few passes, and Slow down lowers it after a pass below your accuracy threshold. The Tempo field stays as your starting tempo.
Echo cancellation, noise suppression and auto gain are turned off so your guitar signal arrives untouched. Plug into input 1 and set the gain so notes appear cleanly without clipping.