This should be the next menu step after you've mounted your root partition, unless you've already performed this step in a previous run of dbootstrap. First, you will be asked to confirm that the device you have mounted on root is the proper one. Next, you will be offered a menu of devices from which you can install the kernel. Choose the appropriate device from which to install the kernel and modules; this will either be a CD-ROM device or the first floppy device.
If you're installing from floppies, you'll need to feed in the Rescue Floppy (which is probably already in the drive), followed by the Drivers Floppy.