A qualified person is someone with the skills and tools necessary to locate wall studs, identify the type of wall structure (wood, metal, masonry), and install screws correctly to the wall structure. Skills and tools include an electronic stud finder, drill motor and bits, screwdriver, and the ability to correctly use these tools.
For all other wall types, a construction professional must install the bed to the wall. A certified construction professional will be in compliance with applicable regulations in the province, state, or country where the furniture is installed.
Your local better business bureau or building inspector can give you a list of local contractors with knowledge of wall construction and cabinetry installation. An internet search for “Home Handy Service” or “Home Furniture Installation Services” may list qualified, professional installers in your local area.