Hey Himanshi, you can run testNG with command prompt by using following line of commands:
C:\Users\Admin\Desktop\Ruksar\workspace\TestNG
set classpath=C:\Users\Admin\Desktop\Ruksar\workspace\TestNG\bin;C:\Users\Admin\Desktop\Ruksar\workspace\TestNG\lib\*
java org.testng.TestNG C:\Users\Admin\Desktop\Ruksar\workspace\TestNG\testng.xml