does anyone know how to update it after the download?
Before you try updating Firefox, can I ask which Linux distribution you’re using ?
If it’s Linpus Lite on an Acer Aspire One … for your own sanity DO NOT uninstall Firefox 2, uninstalling Firefox 2 WILL break your OS irreparably.
That does NOT mean you can’t install a later version of Firefox … it just means you have to leave Firefox 2 in place as well.