Steps for TestNG Installation:
1.Goto Help and Click on Install 'New Software'
2.Enter 'https://dl.bintray.com/testng-team/testng-eclipse/' in Work With field & Press Enter
3.After pressing enter Eclipse will take little processing time And After processing TestNg will appear in Option box.
Select as Shown in above image and click on Next button.
4.If you click on Next following screen will appear.
5.After Clicking on Next button below screen appear.
6.Accept the terms & Condition(TnC) and Click on Finish. Now actual installation process will start as below and wait till it become 100%.
7.If Security warning appears as below then click on 'Install anyway' button
8.After successfull installation Eclipse will ask for restart as below. Click on restart.
9.Confirm TestNG installation by Going Windows > Preference as Below.