It's very easy to change the oil on a Picanto. If you're lucky enough to have a service pit to drive the car over then even better as this will provide you with plenty space to work. The owners manual comes with instructions on changing the oil so if you have it take a look. All you'll need is a replacement oil filter, 3L of good quality petrol engine oil. (I use Castrol edge 5W40), a container to drain the old oil and a socket set.
Start by removing the oil filler cap in the engine then remove the drain plug at the bottom of the engine and leave the oil to drain into a container.
Then unscrew the old oil filter should be easy enough to do by hand can buy a tool if it is too tight.
Put a little oil on the rubber O-ring of the new filter then carefully screw it in.
Put the drain plug back in the engine and fill from the top with 3 liters of oil.
Replace the filler cap and then use the dipstick to see if the level is correct.
Don't over tighten the filter or the drain bolt to avoid damaging the threads if needs be buy a torque wrench to help with the drain bolt the owners manual has the correct torque.