Can't install Guest Additions using VirtualBox, Ubuntu guest OS, Win7 host OS

I'm new to VirtualBox and Linux. I've set up VirtualBox 4.0.4 on Windows 7. Successfully created a virtual machine running Ubuntu server 10.10 64 bit. I'm trying to set up Shared Folders. Prerequisite is Guest Additions. I've followed the Manual, as much as I understand it, and have Googled the heck out of trying to get past this. Here's what I've done:

1. sudo aptitude update
sudo aptitude safe-upgrade
sudo apt-get install dkms
   
2. Devices > Install Guest Additions... (nothing apparently happens, but I hear that's ok)
3. Devices > CD/DVD Devices > [peek at the dropdown: bottom line has Remove disc from virtual drive, so I think that means the ISO is in the virtual CD-ROM drive
4. Change to directory where your CD-ROM drive is mounted and execute as root, so I: cd .., cd .., cd media, cd cdrom. (am I even in the right place?!)

I try sh ./VBoxLinuxAdditions.run and sudo sh ./VBoxLinuxAdditions.run I get

sh: Can't open ./VBoxLinuxAdditions.run

I try bash ./VBoxLinuxAdditions.run and sudo bash ./VBoxLinuxAdditions.run I get:

bash ./VBoxLinuxAdditions.run no such file or directory

I try chmod +x VBoxLinuxAdditions.run and get no such file or directory

It seems I'm in the wrong directory, the right files aren't where I need them, wrong permissions, or wrong commands. I'm totally lost since every troubleshooting point I've seen on Google either hasn't worked for me when it did for others, or I just don't understand the instructions. Thanks in advance for any help.

This is what mount shows

As I mentioned in the comments, seems the ISO is not mounted. Here's what you can do

• Ensure that the guest additions ISO is available to the host. You can do this by clicking on Devices menu -> CD/DVD devices and point to the GuestAdditions ISO file. The Guest additions is available in Program Files\Oracle\VirtualBox folder

• With that mounted, type in the below

  cd /media
  mkdir vbox
  sudo mount /dev/sr0 vbox/
  cd vbox/
  

• Now, the guest installation ISO is mounted as /media/vbox

• Run the Guest additions installer by tying ./VBoxLinuxAdditions.run