Paypal Rest API - 如何获取客户端ID和密码？

I am considering using implementing Paypal Rest API using using Omnipay: PayPal package - PayPal_Rest (Paypal Rest API).

Where do I ask client to find client ID and Secret Key from their PayPal account so they can enter on our backend in order to use Paypal Method for their eCommerce site?

I am even struggling to find one from my personal Paypal Account.