Apply a thick layer of the  cream on the area you want to work on, cover with cling film and all to be absorbed into the skin.
Leave on skin for 30-60mins before wiping off.
Note that the longer you leave the cream, the more numbing hours you get. Best to leave on skin for 1hr before wiping off. 
For tattoo, laser or any deep dermal procedure, best to leave the numb cream for 1hr 30mins. 
Numbing effect last within 3-5hrs. 
Can also be used for brows, laser, waxing, piercing, etc.