How to turn off password to operate phone each time?

Settings>Touch ID & Passcode, and you turn it off there. Understand that turning off the passcode makes your data vulnerable if the device is lost or stolen, and you will lose the ability to use some features that can only be used if the device is passcode locked. Also, if you have a work email on the device, many employers can block the ability to turn off the passcode if you have their mail account on the device.