I have set up my Magento E-commerce website. I have a Paypal Business account but in the moment when configuring Paypal it says: 
[![ThirdParty Permissions Username][1]][1]


  [1]: https://i.sstatic.net/FhTMB.png

Where is Magento 2 can I find or make this username? All I have been able to find are the API settings Paypal gives, which is fine but now I need Paypal to accept my website.