Simply drag and drop the plugin on the timeline. To enter the settings option, once you have added the plugin to the timeline, right click on the colored bar that appears below the timeline track of the plugin and highlight the show option. Alternatively, you can left click the magnifying glass icon that appears on the right side of the colored bar. For the audio plugins, if the plugin is not working at all, you will hear a trouble tone waveform to indicate that. If the value is unspecified, it uses default. If you specify the default, the value becomes unspecified which means that nothing gets sent into the program.
Some of the ffmpeg plugins are not usable with CINELERRA-GG INFINITY due to input/output requirements. Also, some do not come with legal initial supplied values for the parameters (ffmpeg works on filtergraph, while CINELERRA-GG works on stack). These plugins get tested at least once and if they crash, cause problems, or are deemed unusable, they are commented out in the plugin.opts file in the CINELERRA-GG ffmpeg subdirectory. Generally they are not retested so if the ffmpeg software changes them making them usable, they will still not be accessible until the plugin.opts file is changed. You can easily retest these, by temporarily uncommenting the copy of the plugin.opts file in the bin subdirectory and using Settings → Preferences → Interface tab → Reload plugin index
FFmpeg’s plugin guide is at the link: ffmpeg-filters.
The CINELERRA-GG Community, 2021