Would some one pls teach me how to upgrade it?
Generally speaking, you do not upgrade programs, unless the files are supplied by the distro. Then there will be a package to 'upgrade' the original files. These are tested against the original installed files by the distro suppliers.
Next, you can get to the next release, by removing the original, downloading the next version and installing the next version.
To remove the original files, you become the root user, and delete the directory where the files are installed. This can be dangerous for a new user. You need to understand the commands, or gui tools you are using; FIRST.
I usually get the new version from the Mozilla site. I'm running 3.0, the download is an archive, and is untarred in the correct location. Then you will need any plugins such as Java. I get the latest from Sun's download site. They have instructions on the site for install. You will want the Flash plugin as well. Similar to the Java install.
I do all the installing as root, ans as mentioned above, it can be dangerous if you do not know what you are doing.
You will find most distros do release some type of an update, but they lag the release, often by several months.
You do not have to install FF as root user, if your system has only one user that will use the new version. If you install FF as a user, the files will go to your /home/username directory. Understand only your user will be able to use FF, if this is the way you do it. It is safer, in that there is no risk to the system files. You do not have to remove the original. You would have to make a sim link to Java, assuming it was installed for the original.
Think about how you want to install it, post your questions, being as specific as possible. Have a look for the install instructions on each site. To know what plugins are installed now, on the location line in FF type 'about
lugins' ( without the quotes ) and you will get a list of installed plugins. To make the new version work in a similar fashion, you will need the plugins.
Hope this gets you going in the right direction.