Skeletal muscle area

I am new to image J. I can’t acomplish this tutorial ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4767633/figure/F4/) beacuse can t set the threshold levels. I can t understand why…i need it or my license thesis, pls help guys…

Hi,
Did you solve this problem? i have the same problem too. I need this for my PhD thesis and I would appreciate it if you could help.