I want to get Ubuntu on my usb stick, but I don't know too much about computers. I want to be able to put this on my usb stick, but I just want to be sure it will not mess any files up on my computer first off. I have a large number of files on here that I absolutely need. To clarify: my usb stick is empty, I'm only worried about messing up files on my windows computer. Thanks for the help!
Using a tool like UNetbootin (http://unetbootin.sourceforge.net/) To put Ubuntu on a usb will not harm your computer in any way (provided you have told it to write to the usb and not the hard-drive.)
Once you've booted into it, the only way to do any harm to your computer is if you tell Ubuntu to install to the hard-drive. Even then, you can dual-boot so that you can keep your stuff and get to use both Operating Systems.
Hope that clarifies!