Learn how to safely do a back carry with a rucksack carrier with this one up one down (used to be known as the"walk like an Egyptian") method.
The straps are worn like a rucksack and the chest belt remains done up at all times. Each arm is threaded out of the shoulder straps one by one; first one comes up and forwards, the second comes down and back, “one up, one down” method. The chest belt is not a source of weight bearing support so please keep one hand on your baby at all times as seen in the photos.
Baby should be old enough for back carries in your buckle carrier that fits them well. Read more about this here.
Please see your local carrying consultant or sling library for help if you are unsure. It is wise to practice with some help and in front of a mirror the first few times!