There are no such things as "stupid" questions. However if you think your question is a bit stupid, then this is the right place for you to post it. Please stick to easy to-the-point questions that you feel people can answer fast. For long and complicated questions prefer the other forums within the support section. Before you post please read this
bolle: I suggest you read the Mint Guide, available at the Mint Wiki, regarding installation procedures and partitions, especially pgs 10-20. Pretty much all your questions will be answered better than me repeating them here.
To use it just drag the ISO onto the executable, and the readout should be the same as the one given on the download page. Then use your disc burner to burn an ISO. Not a data disc, but ISO. Use the slowest burn setting (Probably 4x), and let it be. Then when installing Mint, simply follow the installers instructions. Good luck.
PS: Don't listen to your sisters BF. He doesn't seem to know what he's talking about. Only flash drives you have to be worried about. And that's not directly related from formatting, but more or less to do with reading and writing to the flash and how many times it's capable of. Different File Systems for those can produce more writing or less writing depending.