To trigger keypress, short together pins B0 and A7.
This variant requires the TinyUF2 bootloader to be installed. This can be downloaded from the tinyuf2 releases page. The F401 blackpill binary works for both F401- and F411-based blackpill devices.
Double-tap reset to enter bootloader mode. Copy the built uf2 file to the device by dragging the file to the new USB disk.