I like to use the word yes every time my dogs are doing something right. You will find lots of websites on clicker training and such that will show you how, I just replace the clicker with the word yes so I don't have to fiddle with clickers and I can mark the sort after behaviour at any time.
I take treats and if the dog is on a loose leash I say yes and reward. If the dog pulls out in front I left about turn and we retrace our steps, if the dog pulls again I left about turn again. Dog soon gets bored retracing steps that it's already smelt and travelled over.
So I would be taking them for two separate walks, Kelpies are dogs that are bred to work out in front of you and away from their handler but are very capable of excellent heeling, I know I bred them for years.
Be consistent, expect to get no further than about two or three house lengths for about a week, walking twice a day.
Join an obedience club they will give you lots of help and tips as not all training methods suit all dogs and handlers
The left about turn is turning on the spot and almost pushing the dog out of your way.