For single lashes, the easiest is to apply with a tweezer. Run the end of the single lash into the glue. Here’s the trick: lightly bring the glue up about 1/4 up the lash itself. Then apply using tweezers. The glue along the lash will help it stick to the lashes itself, thus staying on much longer.
For the most natural look, ALWAYS apply your mascara AFTER you’ve applied your lashes. You’ll find that the mascara usually gets in your way if you apply it first, and it helps to blend in the the false lashes for a more natural look.