[choof]

you should have downloaded an .iso or .img from linux mint's website

you need to burn the .iso/.img onto a dvd or an usb stick (http://www.imgburn.com/ for dvds, http://unetbootin.sourceforge.net/ for usb)

once that's done, restart your computer. down at the bottom, it should give you the key to access the boot menu. this will be either f12 or f2, most likely. at the boot menu, select dvd or usb, depending on what you used to burn linux.

if this is done correctly, you should boot into linux mint live. from here, you can install using the icon on the desktop. follow the instructions there (if you get any kind of error about mbr, select yes, i don't remember specifics but i had the same issue and clicking yes allowed me to dual boot)

once linux is installed, your computer will restart and you'll be able to select either windows or linux when you boot again.