If a Mac app crashes it will generate a Crash Report. Emailing the developer the report file is one of the best ways that you can help the developer fix the issue.
To locate a crash report open Finder (click on the desktop or the Finder icon in the dock).
Click on the Go > Go to Folder menu. Cmd+Shift+G
Paste in "~/Library/Logs/DiagnosticReports/"
Find the crash report that matches the app name and date. Attach that .crash file to an email and send it to the developer.