Soft Close Mechanism for All Roller Slides and Metal Box Metabox Drawers

Just received these, instructions far from clear (and i'm a competent diyer). is there a video showing how to install?

Delivery question : shipping is 10stg to ireland. if i order 6 pairs of dampers will i be charged 10stg x 6 = 60 stg for this shipment

do you need one or two for a drawer?

Could I use these on sliding wardrobe doors?