well it depends on what coral dip you use. You use the dip directions some are 1 part solution to 2 parts water and mix. place the coral in the solution for 5 minutes or so *depending on dip* and then place in the tank.
here is the suggested use for kents coral dip.
Description: Parasite and Bacterial Dip for Corals
Type: Medication
Description: Kent Marine Tech•D Coral Dip & Conditioner disinfects corals and many other invertebrates to prevent the spread of bacterial and protozoan disease • Designed for all stony corals, and most soft corals. • Tech•D is economical to use, each ounce will make about 1½ gallons of dip!
Directions: Note: This product is a dip, for use outside the aquarium only! Place a quart (950 ml) or more of aquarium saltwater in a container, depending on the size of the animal to be dipped. Observe good practice for temperature, salinity etc. Add one teaspoon (5 ml or 1 capful from an 8 or 16 oz. bottle) of Tech•D Coral Dip & Conditioner per quart (or liter) of water in the bucket and stir. Place the coral in the container for 6 to 7 minutes. Remove the animal from the container and place in the aquarium.
HTH
Mike
BTW I would like to say research the coral before dipping some dont dip very well or can be killed by it.