You could try reading the User Manual, which tells you what the HSE crystal is. From section 7.7:

HSE: high quality 32 MHz external oscillator with trimming, needed by the RF subsystem

You could also select the Nucleo-WB55 as your target board when creating your project. This will pre-populate the HSE frequency with the correct value:

And to select this as your system clock source, just select it in the System Clock Mux:

This is the default if you created a project specifically for the Nucleo board.