JUNGFRAU

I am trying to delete files from the Disk Analyzer that take up space on my hard drive? I placed a check mark on the files that I want to delete, then try to do that but I get a message that says: "access denied" I Googled this type of question and saw a response to this, upon checking on it, I don't see anywhere in those postings what the answer to the problem is? Can somebody explain what I have to do to rid my system of those files? JUNGFRAU