Do this by entering the command passwd You will be asked to enter your old password then your new password. Although people tend to do a lot of work in Linux by typing in commands, you can also use a more conventional Windows-style interface if you want. You might want to explore this some time. A few of the games are interesting. For example, Sirtet is a standard Tetris game.
Asteroids is a pretty good implementation of the arcade game.
Sokoban is a puzzle where you have to push all the jewels onto the green disks. The folder icon with the little house represents your home directory. Click on it to see a directory window that contains the files that you own on the math department system. Anything that you put in this directory can be accessed through a Web browser by someone who knows the address. This is similar to Windows.