You will need the Homebrew Channel installed. Use methods like LetterBomb or Str2hax (these are safe, free, and well-documented online).
Important Note: "Highly compressed" usually refers to the archive (ZIP, RAR, 7z). When you extract the file, you will still get a full-sized ISO or WBFS file. If a file claims to be a playable 200 MB ISO, be wary—that is likely a fake or a broken ROM.
For those without a Wii, the Dolphin Emulator is the definitive way to play Edge of Time in up to 4K resolution. Here is how to handle the highly compressed ISO.