There are different ways to secure fence posts in or to the ground, but these are the two we use - using fence post with welded base plates or ones which can be set in concrete.
Fence posts with welded base plates are only suitable for solid ground. These have a 6mm plate welded to the bottom of the post with four 14mm holes, one in each corner of the plate.
Concreting fences posts in offers a sturdier hold and has an extra 600mm which allows for setting into the ground. Both concrete and base plate options of fence posts are 30mm higher than the metal fence panels, leaving a 50mm gap from floor to underside of metal fence panel.
Fixing metal fence panels to fence posts couldn't be any easier. With the way, they are designed you screw the m6 stainless steel button head bolts through the panel into the fence post both have preset holes, so you have nothing to do apart from aligning the holes on the panels and posts and insert the bolts.