The above link didn't work it means you need a higher version of TestNG for the eclipse. Before that check TestNG is installed or not in order to know that press CTRL+N in the wizard you can see TestNG class file name.
If it is not displaying then try installing TestNG In Eclipse IDE Via Offline Jar Files:
1)Download the latest TestNG Jar files from the link TestNg Jars ("https://github.com/cbeust/testng-eclipse")
2)Download TestNG 6.11, Clicking on the link will download the “site_assembly.zip” file for the TestNG version 6.11. This file contains two folders named as “features” and “plugins“.Go to the eclipse installation directory and look for the “dropins” folder there.
3)Create a folder inside the dropins folder and name it as “testng-eclipse-6.11“
4)Extract the “site_assembly.zip” file and copy its contents to the newly created “testng-eclipse-6.11” directory.
5)Restart Eclipse
OR
Go click on Help> Install new Software> Under Available software> Work with textbox paste this "2019-06 - http://download.eclipse.org/releases/2019-06" and then click on ADD. You will now see the files like TestNG and a lot many others. Select TestNG click on Next> Next> Accept the condtions> Finish. It will restart the eclipse. Inorder to know the installation is successful Press CTRL+N.