Had to delete the following text because 'synaptic' package is missing.
Alternative method: Installing the software without using commands
This part of the guide shows how to install the software without using commands. Users who are new to Linux may find this more comfortable. However, note how much trouble is needed to avoid entering the simple command "sudo apt-get install chromium-browser".
Insert a Debian SD card in the Raspberry Pi.
Connect the Ethernet cable from your Raspberry Pi to a modem or other internet service. You may also use a WiFi device, but you may need help to get this working.
Connect the power cable. Log in with your username and password.
Enter the following command and press enter at the end.
Wait for the desktop to finish loading.
Click on the LXDE icon (the strange X) in the bottom-left corner of the screen.
Move your mouse to point to "Other".
Click on "Synaptic Package Manager". Note entries are in alphabetic order.
The Synaptic Package Manager will open.
In the box near the top marked "Quick search" type in the word "chromium".
You should see the list of software change to show only software with the word "chromium" in the name. One entry in the list should be named "chromium-browser".
Click on the box to the left of the entry named "chromium-browser".
Click on "Mark for Installation".
You will see a warning box entitled "Mark additional required changes?". Click on the "Mark" button.
Click on the "Apply" button above the list of software.
You will see a warning box entitled "Apply the following changes?". Click on the "Apply" button.
You will see a progress bar named "Downloading package files". Wait for this to finish.
You will see a progress bar named "Applying changes". Wait for this to finish.
You will see a message "Changes applied". Click on "Close".
To close the Synaptic Package manager, click on the menu item "File" and then on "Quit".
You can now open the Chromium web browser as described above.