To start getting oil up out of your concrete with cat litter simply pour some of it over the stain and work it into the area by stepping on it or mashing it down another way.
Clean oil stain on concrete driveway.
Leave the litter alone for at least an hour before sweeping or vacuuming it away.
Wash away the oil with a strong detergent and a scrub brush or sponge use a concrete cleaner or degreaserto loosen and remove the oil apply a poultice that will break down the oil and suck it from the concrete.
In the bucket mix the detergent with the hot water stirring to combine thoroughly.
If some oil still remains you can repeat the process as many times as needed.
Using a stiff bristled brush start scrubbing the area.