You will discover instructions for how to achieve this from the help files for the specific software.
Ensure that Java is enabled within your browser, and clear the Java cache to ascertain if that fixes problems with a specific game not loading. Add the Pogo.
Ensure your browseractually supports the version of Java you have installed.
Just about the most common issues is Pogo games not working in Chrome after the browser update. If you have the 64 bit version of Java then you will need a 64 bit browser.