How do I use the pagination to get next page based on API documentation for Harvest API

Hello, I have been working on an API call to return pages. I have been successful in creating a query containing a parameter page="&pagenum&" which works but I do not understand how I can use the pagination documented in the API documentation. It looks like there is a reference to rel="next" does this go in the API call with the URL or how do I use this? Many of the API pagination posts do not have the same authorization string that I have to use [Authentication:[ Basic"xxx"]]. I have read about looping and all the typical posts but fundamentally I do not know how to use this to build into an API call. 

Thanks in advance