You must login as a root user, if not root user then switch to root user using following command:

$ su -

Create the directory i.e. mount point:

# mkdir -p /mnt/disk

Use mount command as follows to mount iso file called disk1.iso:

# mount -o loop disk1.iso /mnt/disk

Change directory to list files stored inside an ISO image:

# cd /mnt/disk
# ls -l