You can create an API key from inside Jellyfin at Settings > Advanced > Api Keys.

As of v0.6.11 the widget supports fields ["movies", "series", "episodes", "songs"]. These blocks are disabled by default but can be enabled with the enableBlocks option, and the “Now Playing” feature (enabled by default) can be disabled with the enableNowPlaying option.

    type: jellyfin
    key: apikeyapikeyapikeyapikeyapikey
    enableBlocks: true # optional, defaults to false
    enableNowPlaying: true # optional, defaults to true

Added in v0.1.0