To dispose of used motor oil you can put the used motor oil into the oil container that the new oil came in.
Then put the lid back on and take the used oil to an auto parts store such as Autozone, Oreilly Auto Parts etc.
Some of those places will accept used oil for recycling for free.
Most auto parts stores and even some automotive shops will accept the used oil for disposal either for free or for a small fee.
Or contact your city or town and ask if they have a way to dispose of used motor oil such as taking the used motor oil to the local landfill and they may have a spot where you drop off motor oil, paint etc.
The motor oil then gets recycled and does not go into the ground.