It means, for instance, that non-political or non-governmental organizations in civil society are very useful for democracy : they build social relations, trust and shared values, which are transfered into the political sphere. They help different societies whithout discriminate them on their religions, on their skin colors, or on their government or politics. They help to hold them together and facilitate the understanding and contact.
Citizens participate in the civil society in voting, its a minimum. But it's very important to be conscious of our civil conditions, of our political situation and of our rights. Especially in these times where there is more and more abstention during elections or referendums.
There is no need to know every details and every single things about politic and government life, but for exemple, volunteering is already a start to become more conscious. It makes you realize that you're living in a civil society where all people are connected and have a role in it. Volunteering is often considered as a characteristic of the non-governmental organizations that constitute civil society. This is a beginning to be a member of democracy and to take part of it.