stm32wb55 low power how to?

Good afternoon....

I am new to STM32 land. I have a STM32WB55 board I am working with...I am using 16MHz internal clock source, the I2C module at 100kHz, a timer running with 8MHz and some GPIO interrupts. I would like to know how to go about placing the unit into low power mode such that an event (Timer IRQ or GPIO IRQ) wakes up the system, it processes what it needs to in the while loop then goes back to sleep. I am familiar with how to do this in MSP430 land but not in STM32. Can someone tell me what I need to do to accomplish this? Or at the least point me to the correct videos/ documentation for setting up registers for this?

Thank you

Steve