Summarize this article:

Eyeshadow primer is great because it helps lock your eyeshadow in place, creating a longer-lasting look. In addition, you’ll get a more intense color payoff, and the color will go on more smoothly, so it will be easier to blend. If you don’t have eyeshadow primer, use regular face primer instead. If any of the eyeshadow or mascara spilled onto your cheeks, sweep it away with a large makeup brush. Use big, fast strokes to avoid smearing it into your skin. If you do happen to accidentally smear your eyeshadow, use a cotton swab dipped in makeup remover to erase the mistake, and then use your blending brush to fix any lines in your makeup.

Summary:
Apply a thin coat of eyeshadow primer. Clean off any excess makeup from your cheeks.