The stars are always up. The Earth is surrounded by stars on all sides all the time. We can't see them when the Sun is above the horizon because the Sun's light is scattered by the molecules in the Earth's atmosphere. With a telescope pointed at exactly the right places, it's possible to see stars in the daylight sky...I've done this with my telescope.
Stars become visible after the sun sets. You can find the time the sun sets on various websites, as it changes from day to day with a regular pattern. You'll need to provide your location.
They are always there. They become VISIBLE when the sun has set and the sky is dark enough for the stars to be visible.
They come up at night time, with their friend, the Moon.
