(1) Click the menu button at the top right of Firefox

(2) Click on "Add-ons"

Firefox Addon Menu

(3) Find the "Keywords Everywhere - Keyword Tool" add-on & click it.

Find Firefox Addon

(4) Click the settings icon.

(5) Click "Check for updates". You will see "Available updates" in the left hand side menu.

Update Firefox Addon

(6) The addon will now update to the latest version here