Load your Mission Replay Log
First, ensure you have the SCM, if not go to this page then come back here: SCM
Next load the current running total sheet here:
Leaderboard Running Totals
Now click on the event you need the combat log for
This will open the Google Drive window for that log, download it like this:
Alternatively the log may look like this:
Now, open the SCM and browse to your combatlog and load it, this will normally be in your downloads folder. You can then use the data to improve your build.