You'll see this page when choosing to setup network in the Slackware installation step. Now you need to choose what type of connection you are using. There are three options here:

• static IP - Use a static IP address to configure Ethernet.
• DHCP - Use a DHCP server to configure Ethernet.
• loopback - Setup a loopback connection.

If you are looking for a guide on how to setup ip address for an already running Slackware Linux, check out Linux basic network configuration - Setup Slackware Ethernet ip address tutorial.