Editing Sidebar

For several years now, I have been making monthly edits to the Sidebar on my Homepage without problems. Today, I attempted to make another edit. I get a note at the bottom of the page stating “You need to make this file writable before you can save your changes. See the Codex for more information. I tried ignoring the note, but then the edits aren’t accepted. I printed out the Codex material. It consisted of six pages of text concerning changing file permissions. I am not a computer expert and the text meant little to me, talking about “dhapache” and “nobody”. I am the only person authorized to make entries or changes to my WordPress site. Why do I need to suddenly change file permissions? If such changes must be made, are the instructions written in simple English explaining the process?