Read Getting started for a quick tour of NSubstitute.
For more in depth information start with Creating a substitute.
If you can't find the answer you're looking for, or if you have feature requests or feedback on NSubstitute, please raise an issue on our project site. All questions are welcome via our project site, but for "how-to"-style questions you can also try StackOverflow with the [nsubstitute] tag, which often leads to very good answers from the larger programming community. StackOverflow is especially useful if your question also relates to other libraries that our team may not be as familiar with (e.g. NSubstitute with Entity Framework). You can also head on over to the NSubstitute discussion group if you prefer.