puppy will mostly detect drives connected....
ofcourse easiest way is to click on mount icon in desktop or from jwm menu Filesystem -> 'Pmount mount/Unmount drives' option.
Another step is to check output of "tail -f /var/log/messages" from console which list new devices connected to machine from which you can manually mount from console
For example If sda4 is the one detected...
Cmd syntax : mount <device> <path to mount>
E.g mount /dev/sda4 /root/newdir
to unmount mounted device:
Cmd: umount <path to mount>
E.g. umount /root/newdir
this is jus a sample reference use case.. hope something here may help you....