Get this exact contact cement with the applicator built in the cap
Just clean the board and underside of pad with 70% isopropyl alcohol using a cloth
Let dry a couple minutes
Push pad down and trace outline with pencil
Pull up the pad as much as it can go and apply glue on the board inside of the outline
Now put glue on pad starting with area near the board making your way out until the outer edge
Wait 20-25 minutes for all the glue to dry
Assemble carefully pad to board because once it touches it can't be moved again
Press down with as much thumb pressure as possible every single areas of the pad and especially the edges
Give it a couple hours before going in the water
Good luck
Happy kitesurfing