When you log into the coach dashboard, you should see a tab on the left hand side called "Management". If you click on this, it would take you to a screen where you can view the athletes and coaches in your team. On the right hand corner, you will see an 'Add athletes' button. Please click on this button to then add your athletes emails to invite them, or copy the code that is displayed and send it to your athlete.
Your athlete can add your code if they have a Wild pro account. They can find this option in settings > general.