How do I clean out the smell of gasoline in my garage?

If the smell is coming from the floor try these:

Pour odor-absorbent cat litter onto any area that is still wet. Allow it to sit for an hour or two and then sweep it into the garbage.

Apply a baking soda paste if the cat litter does not do the trick. Put enough baking soda into a bucket to cover the area where the spill was located and add enough warm water to make a paste. Spread the paste over the area and let it dry. Baking soda is an effective odor neutralizer, and you can sweep it into the garbage once it's dry.

Or you can pour dish detergent onto the garage floor. Use a kind that's specifically designed to remove grease. Scrub the area with a brush and warm water and then wipe up the area with a clean, wet rag.

has it been spilled ? is it coming from gas cans? coming from vehicles equipment in garage?

You could pressure wash the floor, there must be a spill if you have the smell.

This is really helpful Lavonne, here you go.. https://www.youtube.com/watch?v=y6rp0pOUCUA

Make a thick paste of baking soda and water. Let it dry and then scrape it up. I have read that dishwasher detergent will also work, but, haven't tried that.