Get ordernr from Netshop web Api

Never worked with Web Api’s and I wonder if anyone can help. I have got a pdf description which is attached as a Zip-file.
It includes a oAuth2 step so I guess it have too be done server side.
some pictures of providers and actions would be nice.

I hope to recieve a Ordernumber and customer number from the web api
External Login APISendaway.zip (131.5 KB)