Head over to bilibili.com and find the music video or cover you want. Right-click the address bar and choose Copy.
Switch to YouTube to MP3 Converter. Paste the link by clicking the Paste link button in the toolbar, or simply press Ctrl+V on Windows or ⌘+V on Mac - the link is pasted and the video title appears in the queue.
Click Start all. The program extracts the audio stream and converts it to MP3 - no video is downloaded, so it's fast and doesn't take up extra storage.
When the status changes to Done, right-click the entry and choose Open in player to listen right away, or Locate saved file to open its location in Finder or Explorer.