There is a STLink on all Nucleos.
Method 1: You have a BIN file, then plug the debugger USB to your PC, and you see the nucleo as memory stick. Drag and flash. like mbed.
Method 2: You use CubeProgrammer with any input file (bin, hex, etc...) connect, load file, program (ahem.. "download")
Method 3: You use debug mode, launch the debugger to reflash with new image, then quit the debugger and the code will run by itself.
Other methods are more "advanced" like if the mcu flash is blank, using the target MCU USB will be another way to flash it (bootloader interfaces)
