Hi
In order to use Apple Pay, your iPhone must have Passcode enabled.
However, you can also set up Touch ID, which you can use most of the time for unlocking your iPhone (there are some occasions when you will still need to enter the passcode, such as after restarting your iPhone).
To set up Touch ID, follow the steps here:
Use Touch ID on iPhone and iPad - Apple Support
Once it has been set up, opening your iPhone to the Home screen can be done by simply pressing the Home button and leaving your (registered) finger or thumb resting lightly on the Home button / Touch ID sensor for a moment.