Step 1 - Open the eclipse IDE, browse on top for the Menu-bar.
Step 2 - select Help -> Install New Software....
Step 3 - You will see the panel for the installation, then you select drop down and select
Indigo Update Site - http://download.eclipse.org/releases/indigo/ as below-
Step 4 - Then type the new software which you want to install (in this case we want maven, so type maven) and select the expected checkbox as-
Step 5 - Then press button next for the successfull installation.