You'll probably find that breeder to breeder is slightly different, but my routine is as follows. I always start at approx 3 weeks, but I start with a little scrambled egg made with goats milk, the Dam gets this for breakfast and once the pups begin to be interested in
her food I give them their own, I find this a good gage as you can waste a lot of prepared foods if they are not quite ready. I've always found them more likely to eat the scrambled egg rather than the complete puppy food to start with too.
My pups get the scrambled egg in the morning just to start with and then perhaps some watered rice and chicken or rice and minced meat in the late afternoon, they seem to be happy to lap these up at 3 weeks. I find they take to these much quicker than their complete food, after a few days of clearing their bowls quickly, I then soak their complete food, which they are happy to eat going into 4 weeks of age. It is good for pups to have a variety of tastes.
( i'll be using burns puppy food mixed right down with water). and how do i do this i.e once a day twice etc.
I'm sure you know already how to prepare the complete puppy food, but just incase as some people are not so sure.

Boil your kettle and allow it to become luke warm, (hot water on the complete food will destroy all the vitamins etc) once luke warm pour on the dry complete puppy food and allow to soak for upto an hour, then mash. As the pups get bigger you don't need to mash and eventually they may eat it dry, (6-8 weeks, some will prefer it, some won't and will still like it soaked) with plenty of water available