The Sea of Stars Community had a fairly simple UI, so I won't go into detail. Most of this chapter's information came from Huiji Wiki. Although that material was already several years old, Paradox Interactive hadn't changed the Sea of Stars Community, so it was still useful as a reference.
Once an empire with neither a gestalt ethic nor a genocidal government had established communications with half the empires in the galaxy, and at least three empires, including itself, had established mutual communications, every empire would receive a notification. Driven Assimilators did not count as genocidal empires. If at least three empires agreed to the proposal, the Sea of Stars Community would be established.
The Sea of Stars Senate was where resolutions were proposed and voted on.
While the Senate was in session, every empire voted on the resolution under debate. Each empire could change its vote once every four months. When the session ended, the resolution passed if the total diplomatic weight of the empires supporting it exceeded that of the empires opposing it. A session lasted 1,440 days.
You could find the Sea of Stars Community icon in the upper right, open the resolutions screen, spend influence to propose a resolution you wanted, and then wait for it to pass. Most resolutions were fucking stupid, though, such as the Tiyanki Conservation Act and tiyanki pest control, which the AI always proposed.
Resolutions passed by the Sea of Stars Community had different effects. Before approving one, read its effects and bonuses carefully, then make your choice with caution.
Once you joined the Sea of Stars Community, every resolution it passed affected your empire. You could find them in the UI and check all the modifiers they applied to your empire.
If you felt it wasn't worth it, you could