Add the pasta shells, water and salt to the inner pot, make sure there is water at the bottom of the pot.
Sprinkle the garlic powder and also add the butter.
Close the instant pot with lid in sealing position and plug the instant pot.
Press on manual and pressure cook on high for 1 minute. It will take a few minutes for the pressure to build up inside instant pot and once the pressure is built (which takes a few minutes and it will show 'On' until then) the count down of the minutes (here 1 minute) will start and it shows the number of minutes left for cooking.
Once the cooking is finished, the pot will beep and you press the 'keep warm' button and wait until the pressure is naturally released and the valve goes down, which will take another few minutes of time. You can carefully do a manual release by turning the lid to the venting position after 12 minutes of NPR (natural pressure release) if needed, if the NPR is not completed by this time.
Once the pressure is all released, open the pot by turning the lid very carefully, gradually and slowly, be very careful while opening the pot as the contents are very hot with steam. Drizzle the olive oil, gently stir the pasta using a good quality spatula to combine the olive oil with the cooked pasta, but make sure not to overly mix.