By default, the command ls won't display files and directories whose names start with a dot. (Many other tools also do this.) To force it to display them, use type ls -a (a = show all files), and it'll tell you if there's a .bashrc. If you're running bash and there's no .bashrc file in your home directory, make an empty one. Then add PS1=[\u] to it, save, and close the console window. Open another, and the change will take effect.
The ~/.bashrc (~ is your home dir) file is a script that's executed each time you log in to a console. The PS1 variable tells the console what the prompt is supposed to look like. If you want to change the prompt, and have it return to normal when you open another console window, you can type PS1=[/u]$ at the prompt, and it will change immediately.
If you think you'll be using Linux as more than a hobby, you'll find a good reference/tutorial book invaluable. We're all on these forums to find and give help, but a book is the best way to get the basics down (YMMV). I recommend "A Practical Guide to Linux" by Mark Sobell.