Using brown mascara on eyebrows can be an effective way to enhance their shape and color, especially if you have brown hair. Here's how you can do it:

1. Cleanse your face: Start by cleansing your face thoroughly. This will remove any dirt or oil that could interfere with the application of the mascara.

2. Brush your eyebrows: Use a brow brush to comb your eyebrows and shape them as you desire. This will also remove any loose hairs.

3. Apply the mascara: Dip the mascara wand into the tube and wipe off any excess product on the rim. This will prevent clumping. Then, gently brush the mascara onto your eyebrows in the direction of hair growth. Start from the inner corner of your brow and move towards the outer edge.

4. Blend it in: After applying the mascara, use a brow brush or a clean mascara wand to blend it in. This will distribute the product evenly and give a more natural look.

5. Clean up: If any mascara gets onto your skin, use a cotton swab dipped in makeup remover to clean it up.

6. Let it dry: Allow the mascara to dry completely before touching your eyebrows. This will prevent smudging.

Remember, it's important to choose a mascara that is safe for use on eyebrows. Some mascaras may contain ingredients that can irritate the skin around the eyebrows. Also, it's better to use a brown mascara that matches your eyebrow color for a more natural look.