Normally in Firefox your Ponder button should be visible to the right of the address bar, like this:
If it does not appear, first check to see if Ponder is installed, but disabled. Type "about:addons" in your address bar, or find "Add-ons" in the Firefox menus.
Ponder should be visible and enabled, like this:
If you don't see Ponder listed on the Extensions page, then you can re-install by visiting Ponder and logging in.
After logging in, a dark install screen will drop down:
Click Install and then follow the browser prompts to approve the installation.
Older versions of Firefox put Ponder on the add-on bar, which was sometimes hidden the "Add-on Bar" by default. First, try updating your version of Firefox by visiting "About Firefox".
To show the add-on bar, go to the Firefox menu, select "Options", and then click on "Add-on Bar". If you can't find the "P" button in Chrome, try these Chrome-specific directions.
Then, you should see Ponder in the bottom right of your screen.