How can I view json file using server key android?

I am new android devloper I do not know how to view json file using server key. If you know I need help. I have given some examples below.

@Headers({CACHE, AGENT})
@GET("api.php?get_ads")
Call<CallbackAds> getAds(
        @Query("api_key") String api_key
);

api_key server key

 public static final String SERVER_KEY = "WVVoU01HTklUVFpNZVRseVdWZDRNbUZYUm5sa1dGcHdURzFPZG1KVE9WVmFWM2hzWkcxc2VtRlhPWFZNTVZKb1lsZHNjMlJJV25WYVdHUjZXREpHZDJOSGVIQlpNa1l3WVZjNWRWTlhVbVpaTWpsMFRHeFNhR0pYYkhOa1NGbDFZbTFXTTJNelFtaGpSMVo1VEcxc2RWcEhiR2c9";

//your Rest API Key obtained from the admin panel
public static final String REST_API_KEY = "cda11Uib7PLEA8pjKehSVfY0vdHsXI269J3MlqcGatWZBmxOgR";