The directions should be in the envelope with the vials. But if not, go to ATI's website - atiaquaristik.com and create an account with a user name and password. Then go to the "lab" sub directory and set up your tank. You'll see a button to "Add new water analysis". The vials have a code on them. You enter the code and that's how ATI knows the water sample is for your tank. They'll send an email (which you enter when creating your profile) when the samples have been tested.
Also, the website is in German, but there's an option on the upper right side of the screen to select English.