Linux assistance part II

Hello peoples. I has 2 Linux questions:

1. I managed to log on OK and even got the network working, praise the baby Jaysus. But when I downloaded an update to Firefox I couldn't find any installer. So I tried to switch to the root user via the GUI and was told no can do that.

Question 1: How do I install new software?



Question 2: What applications would you recommend for net stuff and graphic stuff?

tanks