Firstly, we recommend checking the weight of your child - this helps you know which size will be best.
Before you put the pants on your child, or before they put them on themselves, fold the pants in half lengthways and rub them a few times. This helps to soften them so they'll better mould to the body and stay invisible under clothes.
Once the pants are on your child, make sure the leak guards around the leg holes are flared upwards towards the waistband. This makes sure you'll be protected against any leaks.
You can also check the fit of the pants when they're on your child to be sure the waistband and leg cuffs are fit snugly against the body, and aren't too tight.