creating a loop

I'm using Musescore on an iPad Air and am having a hard time creating an accurate loop to practice with. Are there detailed instructions somewhere on how to do this. Pressing my finger on the measure I want the loop to start seems to start a loop from the beginning of the song, not the measure I want.

While I'm griping, it sure would be nice to see measure numbers and be able to navigate easily in the "Practice" mode!

Thank you!
Andy