Frequent question so a couple of pictures to illustrate how threaded eyebolts are typically fitted.
Actual position in load bed of truck isn't crucial as long as somewhere roughly corresponding to hooks on underside of camper
the only important placement issue is they need to be far enough apart width-wise that the camper loads in between them,
these eyebolts (or something quite like them) need a generous eye for you to hook a turnbuckle down from camper and in to
These are sold with long thread on them, you won't need all that, so once you've drilled a hole in load bed and tried eyebolt together with generous plate washer or similar on underside, you can hacksaw off excess before fitting
(check for wiring/pipes etc underneath before drilling)
typically campers are sold with some form of turnbuckle which links camper/truck,
hooked both ends on, then tightened by hand these will hold your camper on all but severe off-road use.
probably need a shackle between turnbuckle and eyebolt
https://www.ebay.co.uk/itm/251642699089 ... SwN8Ja5BbT
Our members have gone a step further with same eyebolts dropped down through loadbed directly into chassis rail though often not actually drilling holes in rail itself and weakening structure, rather by welding a bracket on rail side and bolting to that!