New Member Network question HELP!!!

Hi Everyone just joined, having a problem with my network have a motorola SBG6580 Modem/ wireless Router in bedroom in one corner of my house 3 computers Hard wired to it, I want to get wireless Access to my garage, by using my D-Link DIR-615 Router hooked to my living room computer that as earlier mentioned is hard wired to the SBG 6580, that should give me the range i need to the garage one room over, Now that all sounds great in theory but how is it done i dont know anyone who can help would be great i just want to use my nexus 7 in my garage, oh i also have 1 slinglink turbo, if i can use that i dont know if it is possible or if i even would need it, thanks...