How do I get my 2 linksys wireless n routers to work together on my home netork?

I already had an existing wireless network in my house with a linksys wrt300n but i had some dead spots in my basement. So i purchased a linksys wrt120n to put in the basement to cover withe area but i cannot get them to work together. The modem and the 300n are on the first floor with an ethernet cable running through the floor to the basement into the 120n. If i plug it into the internet input i get no signal form the router but if i but it into 1-4 inputs i get a full signal with internet connection. The the name of the network remains Linksys and i cannot access the settings to change the name or secure the network. What can i do to make them both act as 1 big widespread router?? Someone please help me i've been at this for days i think i've tried everything. I wont even mention customer service!