We will follow the below steps to install TestNG in Eclipse IDE .

There are two ways in installing TestNG in Eclipse

First Way on installing Eclipse is using "Install new software" option.

Second way is using "Eclipse Market Place". - This option will be available in new versions of eclipse.

NOTE: If your using eclipse latest version, please use Eclipse Marketplace option which is very simple, explained at the bottom.

Steps to Install Eclipse using Install new Software:

Step 1:
In Eclipse, on top menu bar, Under Help Menu, Click on "Install new Software" in help window.

Step 2:
Enter the URL (http://beust.com/eclipse/) at Work With field and click on "Add" button.

Step 3:
Once you click on "Add", it will display the screen, Enter the Name as "TestNG".

Step 4:
After clicking on "OK", it will scan and display the software available with the URL which you have mentioned.

Now select the checkbox at TestNG and Click on "Next" button.

Step 5:
It will check for the requirement and dependencies before starting the installation.

If there is any problem with the requirements/dependencies, it will ask you to install them first before continuing with TestNG. Most of the cases it will successfully get installed nothing to worry about it.

Step 6:
Once the above step is done, it will ask you to review the installation details. If your are ready or Ok to install TestNG, click on "Next" to continue.

Step 7:
Accept the Terms of the license agreement and Click on "Finish" button.

Thats it... It will take few minutes to get installed.

Finally once the installation is done, you can if the TestNG is installed properly or Not.

Go to Windows Menu bar, and Mouse Over on "Show View" and Click on "Other" at the last as in the below screen shot.

Expand Java folder and see if the TestNg is available as in the below screen shot.

UPDATE:

Now eclipse is coming with Marketplace plugin by default which is a rich client solution for installing solutions listed on Eclipse Marketplace directly from an Eclipse. We can easily find third-party plugins that users can add to their Eclipse installation by using search option.

Under help menu, we should have an option as 'Eclipse Marketplace..'. Click on it.

Enter text as 'TestNG' and click on GO to search. You will now see TestNG with install option (If TestNG is already installed, you will have 'Update' and 'Uninstall'. as in the below screen shot)

Hope this tutorial helps you in installing in your machine. Happy Installing TestNG