Actually this documentation is in progress. Some of the features aren't described in the Wiki
The NuGet page is https://www.nuget.org/packages/XSide.System.Extensions/ To install it, from the Package Manager Console, run:
PM> Install-Package XSide.System.Extensions
The toolbox has only one namespace: System.Extensions. Adding a using to this namespace all the extensions will be available.
using System;
using System.Linq;
...
using System.Extensions;
...
namespace My.Namespace
{
class Program
{
}
}
WIP