Take the bottle of Orangeade/Orange soda and pour 1/3 from the bottle (you can drink it if you would rather).
Then pour the bottle of dark rum into the bottle of Orangeade/Orange soda!
Turn the bottle upside down then right way up a few times so the two drinks mix (carful not to shake it), then simply drink it from the bottle (or pour in to glasses i you don't want to look like a piss head)