How to install Mac X 10.6.8

I'm taking a college class. Have an assignment to install Wireshark and report on results as a learning experience. Have a Macbook with X 10.6.8. Tried to run the 64-bit version, and knocked out my modem. Will next try the 32-bit version, old stable version. Need some coaching so I don't knock out the modem again. If this has to be run in binary only, then I'll probably not be able to complete the assignment.