It's quite straightforward. Just fo to "File>Save Job As" on the toolbar at the top, then choose to save as a .maj file instead of a .esj file. You usually have to restart ESTmep at this point. Open the save .maj file which should use the updated database. Re-save as a .esj file by using "File>Save Job As" from the toolbar. Anything you change on a .maj file will effect the overall/latest database, hence why it's best to re-save as an .esj file.

Hope this helps.