How do you feed train?

1) you buy them already feed trained.

2) you build fish cages, place young fish in the cages and acclimate them to eating pelleted fish food. You buy different sizes of fish food as they grow larger, feeders to feed 'em or have the time to feed them a couple times a day. You sort out the fastest growing, largest fish once a month or so, so the smaller ones aren't bullied to death.

It's not a simple process to feed train your own fish - it takes a pretty dedicated comitted pondmeister.

edit:

If you already have the fish in the pond, you can throw food in the pond and hope that they feed train themselves. That works best if you have an automated fish feeder. For the best rusults you should feed in the same place, at the same time EVERY day to get them acclimated to the food. The problem is that if there is a ton of natural forage in the pond, they might never feed train. Not many people have that rigid of a schedule 7 days a week, EVERY week that the water temps are above 60 degrees.