Open the Mp3tag program. Click "File" and select "Add Directory." Choose your music folder or directory and click "Open."
Click the MP3 file you want to edit metadata for. The files will appear in the program's center screen. The current metadata will appear in the left pane.
Edit the MP3's metadata in the left pane. Replace the existing data with the desired data.
Click the "Save" icon to save the changes to the MP3.