Setup is required in both .NET and Salesforce
Salesforce
Follow the process of creating an API user, or editing an existing user, as outlined in the S4S documentation. You will need to change the names from S4S to G4S.
.NET
G4S is distributed as a zip file containing libraries. The package contains the following elements:
• G4S provider assembly files
• Help files
To install and use G4S, you need one of the following:
• .NET based application with access to the code files
• .NET based web application or website with access to the code files
Referencing the library DLL’s
Copy the dll’s to your .NET solution then reference them in the normal way.
.NET → Project → Right Click References → Add reference