Flushing DNS Cache is important when a website is not working, or pointing to the wrong server.
For example, if you've changed hosts, you'll want to clear your DNS cache to speed things up (on your end only).
1) Close all web browsers such as Internet Explorer, Chrome, Firefox, or Edge
2) Click the Start or Windows button at the very bottom left of your screen
3) With your keyboard, type cmd
4) You should see a result called "Command Prompt". Now right click it and then click "Run as Administrator". (If a box pops up asking Yes or No, click Yes.)
5) You should see a black screen with white text now. If not, start over.
6) Type ipconfig /flushdns and then press enter
7) Now close that window and you're done!