Activate the 2nd button from the left (with the two arrows indicating the loop) in the bar at the bottom.
The button turns green.
Set start and end position (note: the loop repeats at the position just prior to the end-position).
In settings (gearwheel, upper right corner) you can control the playback speed and if the loop should repeat without change of tempo or ramp up with tempo increments between repetitions until a final tempo.
Press on the green gearwheel symbol in the upper right corner.
Choose the last line entitled “loop”.
Activate counting in if required.
Choose one of the presets.
Or customize with the three wheels: choose the relative tempo change (relative to the tempo of the piece, in %) at the start and end of the ramp, and the increment from repetition to repetition. Note: the tempo stays constant during a repetition.