In my experience, each of these wg (and the open source community in general) are self-contained and self-organized. You participate by “showing up” (join the mailing list or whatever communication channel they have).
Many of the wg/community are “reactive” or mostly just reacting to things. For example, If someone in the community raised an issue/problem, then people will respond, but otherwise you might see the mailing list to appear inactive.
Is there a specific topic, or an issue in the community that you’d like to help with?
Also, just in case you haven’t already found it, the PSF wiki and the particular workgroup’s charter listed there has more information about joining and communication.