There's nothing more to do, just breathing in and out. Soon the mind becomes peaceful, the breath refined. The mind and body become light. This is the right state for the work of meditation. When sitting in meditation the mind becomes refined, but whatever state it's in we should try to be aware of it, to know it.
Mental activity is there together with tranquillity.
There is vitakka. Vitakka is the action of bringing the mind to the theme of contemplation. If there is not much mindfulness, there will be not much vitakka. Then vicara, the contemplation around that theme, follows. As we go deeper we are constantly aware of the state of our meditation, knowing whether or not the mind is firmly established.