To charge your hoverboard, first ensure that you have plugged your charger into a working wall outlet, so that the light on the charger will illuminate green/blue. Next, plug the other end of the charger into the charging port on your hoverboard.
Most hoverboards have a lithium-ion battery that charges faster than lead-acid cells. Cheaper hoverboards take about 4-6 hours to charge on average, mid-range hoverboards take 2-3 hours while the ones on the higher end of the spectrum take about 1.5 - 2 hours.
When first plugged into the wall (and not into the hoverboard), the hoverboard charger's light should be green. Then, when it is plugged into the hoverboard, it should turn red (if the battery needs charge) or remain green (if the battery is fully charged).