Assuming /dev/sdb1 partition was earlier created with fdisk ..
and is to be mounted on /disk2
# cd /
# mkdir disk2
# mount /dev/sdb1 /disk2
or if need to specify filesystem type
# mount -t ext2 /dev/sdb1 /disk2
to mount permanently at boot time, add into /etc/fstab
/dev/sdb1 /disk2 ext2 defaults 1 2