As has been said, it's best to place the plany outside and let nature take its course.
However, if you INSIST on feeding them yourself, there are a few rules of thumb to follow.
1: BUGS ONLY!!! No people or pet food whatsoever. Ground Beef is too rich and will cause the trap to die and rot.
2: Any bugs you do offer should only be about 1/2-1/3 the length of the trap it's going to be placed in. Any bigger and the trap will not be able to close completely on it, preventing it from forming a seal and causing rot due to bacterial growth. The same can be caused by bugs with long antennae, legs, etc.
3: ONLY feed Live Insects. The trap will close when any combination of 2 hairs is triggered, but the actual release of digestive enzymes and sealing of the trap is only triggered by continued stimulation by the insect struggling within. Yes, nature is cruel.
4: Don't manually feed too often. Each trap is capable of closing and reopening about 3 times before it dies. Tease Sparingly.