There couldn't be anything easier than creating kefir. There are a few important notes to follow. Sterilise the jar you will use and make sure it is cold before proceeding.
Add the milk and the grains to the jar and stir quite vigorously.
Cover with something breathable like a coffee filter or baking paper and secure with an elastic band. Leave on the kitchen counter for at least 48 hours. Stir it if you wish, it is good to see what is happening.
Strain the milk from the grains through a sieve and either make another batch or return the grains to your keeping jar, cover with milk and refrigerate.
If you wish to ferment further, leave the jars or bottles of reserved kefir on the kitchen counter for up to another 2-3 days. It will develop a mild fizziness at this point.
Refrigerate and use in recipes or add to your diet as directed. The kefir will keep in the fridge for up to 12 months without spoiling.