I'm sorry if I'm too late.. but I'll try my best to help
1) so first of all put your compass point on X or W then draw and arc make sure it's more than the middle and not less
2) once you're done put the compass point on What and draw another arc, without making adjustments to the compass because if you do the measurement will be incorrect
3) use a ruler and draw the line in the middle
if you don't understand you can refer to this link: https://youtu.be/3v5HL5nmrJE
