i bought this bec http://www.graysonhobby.com/catalog/...ec-p-2517.html and the way i wired it was a seperate battery. For some reason this ubec has two wires to go into the reciever but i only plugged in one of the to the bat/bind spot. Do i need to plug in both through a y-harness? when i put in the battery nothing happens. Idk what it could be this is my first time putting a bec in a plane and idk whats wrong

I'm not sure I understand... the UBEC in your link shows one set of wires without a connector (you'd connect your flight battery to those wires) and one set of wires with a servo connector on it.
(you'd plug that servo plug into your receiver, into any unused receiver port.)

what you're describing (but NOT what is shown in your picture) sounds like a dual / redundant battery regulator... meaning you would connect TWO separate flight battery packs, (the redundancy is if one battery pack dies)
in this case, you'd still only have ONE plug to plug into the receiver.

What he said... Here are some pictures and a good explanation on a UBEC:

http://www.squadronforum.co.uk/showt...-External-UBEC