1. Go to www(DOT)realmofthemadgod(DOT)com/version(DOT)txt and copy the number
2. Go to www(DOT)realmofthemadgod(DOT)com/AssembleeGameClient(enter that number here)(DOT)swf
3.1. If you're using Chrome, click the three vertical lines in the top right and click Save Page As
3.2. If you're using Mozilla Firefox, should be the same as Chrome.
3.3. If you're using IE, what the fuck are you doing with your life?
Should get you the latest client.