You need a glue suitable for the skin (I recommend the spirit gum, I personally use the Kryolan’s one. DO NOT USE SUPER GLUE OR SIMILAR. USE ONLY SPECIFIC GLUE SUITABLE FOR THE SKIN) and then apply it on the back, only on the external border of the mask. Be sure the glue won’t touch your eyebrows or beard (it could be a bit painful to remove later). Follow the instruction of your glue and press firmly the mask on your face in the wanted position aaaaand done!
–GLUE NOT INCLUDED-