You want to pre-scent the room which is achieved by leaving the container with the feeder near the enclosure for an hour
If you buy your feeder you want to use that pre-scenting time to give food and water to the feeder
When ready to feed you want to hold the feeder by the base of the tail and drop it in the enclosure (I do not recommend tong as they hurt and stress the feeder)
Remove if not eaten after 10 min (usually the majority of snakes will immediately grab and coil, if they do not do it in the first 5 min they will likely not do it at all)
The key is to have a well fed, well hydrated, stress free feeder and to feed an appropriately size prey.