I´m try to use the library to make enveloped Data compatible with RSA/PKCS#7 standart. When I can find some help to do it? I´m using C# to make it.

Thanks,
Daniel

A good place to start is MSDN [http://msdn.microsoft.com/library/en-us/security/security/about_cryptography.asp]. You can use the .NET interop services to call into the Windows cryptography API.
Alternatively, you can wait until the next version of .NET comes out; this new version will support enveloped data.