I've just installed Slackware 10.2 that went really well, I Started X without any problem. Now my question is, I want to start installing all my apps (IE Firefox, Amsn) Where should I put the files and How for every users and root to be able to access it without any problem.

Firefox is now available for my user Lorio since it's in /home/lorio/firefox, and to run it I just have to ./home/lorio/firefox/firefox, but I plan to create some more user accounts for my familly on this computer and I don't want to have to install it for everybody!

Thanks in advance for your help.

a good place to install software is in the /opt or in a subfolder in /usr/
firefox and Amsn should already be installed. any user you create, and add to the 'users' group, should be able to access these applications without any further setup, through the KDE menu if your using KDE.

if I wan't to Update firefox to the latest 1.5.0.3 what Is the best way?

download the .tgz file (preferably from an official slackware-current repository, in the xap directory)
use 'upgradepkg [packageName]', see 'man upgradepkg' to learn how to upgrade packages, its pretty easy. its been recommended to backup configuration files before you upgrade, but thats up to you.
good luck