Select the checkbox
Click "Login with MyGuide"
Search for your org and click "APIs & Services"
Make sure you have organization key & secret key generated, if not then click on Generate Credentials
Select the relevant radio buttons to enable Key type, Anonymous access & jit provisioning then click on create
Click the lock icon which actually is API secret controller
Make sure that the checkbox is selected
Click "Save Application Settings"
Click "Ok" to validate the authentication
If you add a new app, you need to ensure that org key and secret has that app, so please do follow the same process to assign it.