Help configuring a static IP on wireless Mac office

I have business service with comcast and a static IP. I need help with how to configure the new static IP on my home office. I have 2 wireless macs and a 1st generation airport extreme. I don't understand how this works, but I have the settings, I just need to know where to plug them in. The Comcast modem is already set up for the static IP but right now, and I have internet access, but my computers are still using a dynamic IP.

Do I configure the Airport Extreme with the static IP or the computers? And do I use the "usable static" they gave me?

How do I do this? Tech support (even signature support) seems to have very limited experience with the Mac OS, especially when it isn't plugged into the modem. So again my issue is how to set up the static IP for an office with wireless macs.

Thanks!