How to get Client ID and Secret in the settings of PayPal :
You have to be to open a business account with PayPal !
Go topage https://developer.paypal.com/developer/applications/sign in and click "Create application" as shown below:
Then enter the name of the application, select a test account for the sandbox that you want to use (if new account, leave the default value) and click "Create application".
After creating the application you will be given your sandbox and the client ID and secret code which will look something like this:
These credentials are what you will use when accessing the API of PayPal to authenticate your app and make requests. Paste them into the settings of your wallet. To switch to battle mode, the keys work in Live mode