I am so frustrated by this!

I have been wanting to set up the internet on my DSi for a while now but I have not been able to and just the other day I was trying to figure out the problem to set it up on my Wii (testing it on my DSi before dealing with that headache)...and support.nintendo is crap...so I am hoping one of you can help me...

I have a Linksys (Cisco) Router

After putting in the security key it said it was unable to obtain an IP address...

So looking on support.nintendo...I manually typed in the IP address and all the other techie lingo...and I got that it was unable to connect to the internet...

I'll be quite honest and say I don't know what the hell I'm looking at when I mess with this crap so I'm sorry if it's not very clear...but I am so frustrated and confused...

Please help anyone! Thank you advance