How can I get rid of a scar using a laser?

By having God do it. It's a common misconception that lasers can circumvent the normal eventualities and exigencies of the healing of the human body. Once a scar is created it is present ever after. The remodeling of the skin can result in one with such a fine line that the typical human can't perceive it at a conversational distance but this has more to do with the skin physiology of that individual than it does w.
Many laser goals. Lasers can accomplish many goals such as remodeling, resurfacing, vascular ablation, etc. Depending on the scar characteristics, some lasers may provide improvement in appearance and sometimes more than one laser may be requires.
Resurfacing lasers. You can never get rid of a scar but you can improve upon the appearance of the scar greatly by using resurfacing or ablative lasers such as co2, fractional co2, erbium:yag, or fraxel lasers.
Probably can't. Laser are helpful in reduction of scar appearance but will not completely remove scars. Seek a laser center near you to determine which type of laser would be best suited for you, and the chance of improvement.
You can't . You can change the color to better match the surrounding skin disguising it better, but the scar will remain.