Well... the condition is explicit enough, but i'm sure you need some more informations !
"Different factions" = 3 factions
A faction match's round lasts a week, so, you'll need approximatively 2 or 3 weeks to have it
Here, in France, the round ends Monday at 1:00 AM, if some people could tell us when it is in other countries of the world, that would be cool. (Well, check the comments, thanks to Teh Paralyzer)
When the round ends, you'll have to choose a faction for a week, just choose an other one
I advise you to play at least a match with this faction, it's better to be prudent.