Problems with an Airport Express and Extreme

I have an iMac and a Macbook. When I purchased the Macbook I bought an airport express to accompany it. I already had a verizon all in one router and modem piece, but I was told that the Airport Express would be helpful. I got it all set up, and it worked great, however it didn't have the range that I'd hoped for. I looked it up online, and realized that it was designed for smaller homes and dorms. I then purchased an Airport Extreme, and I have since set that up as well. However, that one doesn't have any better wireless range of internet. Is this normal? I then attempted to use my airport express to extend my wireless network, however I couldn't get the express to register at all when I would plug it in. All it would do is flash amber. What am I supposed to do to get it to register on my laptop and furthermore how do I use it to extend my wireless network?
Thanks.