You can see a list of members and any pending invitations in Settings > Organization. You can also find the organization owner and invite additional teammates from here.
Only the owner of the organization can remove people from the organization. If you need to remove someone but you are not the owner, ask the owner to do so.
If you need to leave an organization that you are not the owner of, you can do so from your Personal settings.
If you are the organization owner, you can also upload or update your company logo. In the future you will also be able to update your team name. If there are other settings you'd like to be able to update, let us know.