Since you're in Slackware, you're going to have a difficult time working with RPMs. You should try converting your RPM to a slackpack (.tgz):
#assuming this is the correct file name.
Then, cd to /usr/src/linux and type pkgtool
. From there, you can install the package using Slack's package tool. You can specify the path to the directory where the file was downloaded. Follow the instructions, and smile as it does the work for you.
EDIT: Oh yeah, you should probably be root while doing this.