Having my sweet Nikon Z50 is a great thing, and happy to have and explore it’s FLASH!
This little built-in flash can be popped out by sliding small button next to view-finder, on its left. Looking at its settings, flash is set to TTL by default but it has to other modes, just the flash modes itself, such as fill flash, red-eye reduction, rear-curtain sync, and flash off.
To find how to set FEC (flash exposure compensation) it is pretty simple, just have to go to Photo Shooting Menu > Flash Compensation. HFEC can be set from highest +1.0, to lowest -3.0.