well it is symiltanios turns.
you dont realy need anything else. except to put
http://seiv.pbw.cc into your favorates
once you have signed up there click the game lisings (attack button on the left) then click "Currently Open Games" (button in the middle, looks like a fleat with a sun)
scrol down the list till you find "PvK's Proportions Game #1"
and select the empire which you want to take over in there.