unscrew the little stem valve, it will remain on a small metal stick
screw the adaptor onto the stem
with the lever down, place the pump head onto the adaptor
raise the lever
pump air
lower the lever again and remove the pump head
unscrew the adaptor.
if necessary, as the adaptor clears the threads so you can see the small stem, then grab the stem with needlenose pliers as soon as possible, then continue unscrewing the adaptor