How can I set the idle speed?

Hello,

The idle speed on this vehicle is not adjustable.
There might be some other issue that is triggering the high idle.
It could be due to a faulty throttle actuator or the throttle position sensor.
If the check engine light is illuminated, it will be a good idea to scan and retrieve the code(s).

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

You mentioned this happened after the water pump was replaced. Did this issue exist before?
Were there any other components that got replaced or removed while the water pump was replaced?

Please let me know if you have any questions.
Thank you.