Help to sleep and wake up on interrupt

I am using my board with STM32L081KZ.

I set up irq like this:

gpio_init_int(GPIO_PIN(PORT_A, 0), GPIO_IN, GPIO_FALLING, hall_handler, NULL);

How can I fall asleep now so that consumption is as low as possible and the mcu wakes up on my interrupt?

I read Layered PM Infrastructure and no understand how to use it.

In order to use this module, you’ll need to implement pm_set(). - How to implement?