At the dish.
You cant just split satellite signals off to two receivers like you can with normal aerial signals (and even that's not advised)... you need to run an entirely new cable from the dish.. The LNB on the dish might have a spare connector on it if you're lucky, if not you need to replace it with a dual or quad LNB.
As a note on the above... to use a dual tuner freesat recorder each box needs two cables from the dish, so for two freesat recorders you'd need four cables in total (two to each box), which would mean you need a quad LNB... if you're going to run one cable from the dish to the new location you might as well run two while you're doing it so even if you don't want to use a recorder in the new location the cables are there ready if ever you change your mind.
Quad LNBs don't really cost any more than dual ones and the cable is pretty cheap to so it won't cost hardly any more to run the extra cabling.
Amazon.co.uk User Recommendation