A players athlete one ID # can be found by the players photo when you select a player from anywhere within your club account. Below is an example of one way you can view their ID #.
Step 2: Select 'My Account' from the left hand navigation > then select 'Club Account' > select your club
Step 3: Click on 'Club Details'
Click on 4: Click on the type of team the player plays for
Step 5: Click 'Search' in the upper right hand corner > Select the player
Step 6: Under the player's name, you'll see their athlete one ID number