Teach the indication away from the search to start with.
What type of dog do you have and what type of indication do you want.
I like a freeze indication so the dog will have his noise on the scent and not move at all(well the tip of his tail wags!)
You can train a sit indication - I use a sit indication on dogs that are searching for dangerous substances eg explosives. You do not want your dog to touch these obviously.
If you are doing this for fun and may want to enter competitions the freeze is the quicker indication and the most accurate to the exact position of the scent.
Stage 1
I always start with a nose touch to my hand. Just put the palm of your hand near the dogs nose the dog will move towards your hand click put treat into the hand the dog touched and reward.
Over time when the dog is happy to touch the hand you can increase the time before you treat. This is encouraging the freeze behaviour. Your dog will keep their nose on the palm and in a still position until you release.
Stage 2
Hold a large empty yoghurt pot and see if you dog will put his nose into the pot reward and treat. Same as with the hand touch you can increase the duration the dog has his head in the yoghurt pot before you reward. When the dog is very happy with this
Stage 3
Get two yoghurt pots and make small holes in the bottom of one.
Put the scent in the first yoghurt pot and then place the second pot with holes inside the first pot. So the scent is between the two pots.
Ask for the dog to put his nose into the pot - he should be happy with this now and you are adding the scent to the behaviour. Click and reward for a good freeze.
Stage 4
Hold or put the yoghurt pot with scent in different positions - some dogs find this stage very hard so expect slightly less duration to the freezre
Stage 5 start hiding the yoghurt pot in different locations, best to make sure the pot can not be moved and increase the duration of the freeze.
Stage 6 remove the pot and only put the scent in a location and you should now get a freeze.
Watch at the height your dog likes working and stick with this before adding extra height or lower searches.
Dont use too strong a scent it does not help the dog but can overwhelm some dogs. So strong scent is not necessary easy for the dog.
Another way to do all of the above is to use a target. A small pringles lid on the floor and encourage your dog to nose touch it. Again when happy with this you can increase duration so you get a sustained touch and the beginning of the freeze, then add scent to target then hide target etc as above.
Do not at any time add a verbal command to the freeze.
I will search out some videos to help.
Enjoy your searching - dogs love it