Pull data from a REST API Authentication

I'm trying to pull data from REST API. At the moment I'm facing some difficulties tyring to authenticate.

All I have is:

Link:

https://service4.ultipro.com/services/EmployeePerson 

Authorization Headers:

"Authorization: Basic c29tZXVzZXI6c29tZXBhc3dvcmQ="

"US-Customer-Api-Key: ABCDE"

I get this Error when I click OK:

Details: "The 'Authorization' header is only supported when connecting anonymously. These headers can be used with all authentication types: Accept, Accept-Charset, Accept-Encoding, Accept-Language, Cache-Control, If-Modified-Since, Prefer, Referer"