To set the sport level to a client look for the client on Client -> Clients.

  Once there click on  to enter the client's file

Then go to the section Game Information in the client's file and click on the Game Level tab

Here you can select the sport to set the level and click on the checkbox if the client is federated on that sport, and also set his/her position in the ranking manually. 

 To set the level press under the information section

 Once you're done click on Update to save the changes