If all options are correct, click the "Check Default War Assets" button.
Test them by enabling them and checking a few boxes, wait at least one second, and then close and re-open your browser. All modern browsers should support both as advertised, but they are disabled by default in case your browser doesn't support these features.
Note the options for auto-saving and floating EMS score.
If left at defaults, all possible assets/missions will be shown, but by doing this, non-applicable ones will be hidden.
(Optional, but recommended) expand options and select your DLC and previous choices.