Sounds like you are having a hard time, indeed.
Let‘s assume your opponent starts a match. Then the procedure would be:
1) He selects Scenario, Difficulty and side, enters his password, saves the file and sends it to you. Mail or Dropbox does not matter:
2) You receive the file, move it to your inbox, start it from „saved game“. Then you should be asked to set YOUR password (Important: The password is “Caps Lock” sensitive). The file is saved (should be number 2 now) and you return the NEW file from the Outbox to your opponent.
3) Your opponent receives it, copies it to his Inbox, starts the game from „saved games“ and enters HIS password. Then he should be in the set-up phase. After set-up, he presses the red button, waits until the file is saved and returns the new file from his Outbox to you.
4) You receive the file (should now be number 4), put it to your Inbox, start the scenario, enter YOUR password and now it’s your set-up phase. Remember, in the set-up phase, you can set-up, give first movement orders and plot first artillery strikes (if you have off-board arty). When you are done, press the red button and return the new file to your opponent.
5) Now it should be his time for the first regular turn.
Good luck and have fun!