Reporting Crashes

Depending on the OS, there might be an easily accessible log, but they are seldom very helpful. More important is to see if the crash is reproducible - if opening the same score again and doing the same thing again causes it to crash again. If so, then you would post the score and the steps to reproduce the crash, either here or directly to the issue tracker (eg, "Help / Report a Bug" from within MuseScore). If you can't reproduce it, then maybe still post the score here and describe in general terms what you were doing when the crash happened, and maybe someone will recognize it as a known issue, or decide to play around and see if they can find steps to reproduce the crash.