To highlight with a concealer make sure the shade of the concealer is 2 shades lighter than your natural skin tone. You do not want it any lighter to avoid raccoon eyes.
To hide any blemishes make sure to use a small brush to target the blemish only and blend around the blemish with the foundation brush.
For highlighting under the eye dark circles; you can use a concealer brush, a foundation brush, a duo fibre brush or you can use your finger to blend out the product with the warmth of the skin to skin contact for a more natural look.
When you are looking for highlighting concealers, it is best to look for those that are dewy, shiny (for a glow), and with a lighter finish look – (MAC Prep + Prime is an excellent example for this).
To hide your blemishes with a concealer make sure to apply after your foundation and not before to make sure it is not rubbed off with your foundation brush. Make sure to always blend your concealer to give a one-tone look.