Clearing your Firefox’s browser cache is really quick and easy.
Please follow these steps.

Depending on your current settings in Firefox, the screenshots may not exactly reflect what you see.

Step 1: Go into Options

Click the Menu Button on the top right (It looks like three bars stacked on top of each other)
Then click the “Options” button or “Preferences” button.

–OR–

Step 2: Enter the Privacy & Security area

Click “Privacy & Security” on the left side menu. This may be white or blue depending on your browser.

Step 3: Clear data

Look for the section that says “Cookies and Site Data,” then click “Clear Data…”

Check “Cookies and Site Data” and “Cached Web Content”, and click the Clear button to complete the process.

Your Firefox cache is now clear!