It doesn't look like there's a binary distribution of the Opus .lib for Windows, only pre-built encoder and decoder tools, so you'll have to build it yourself.
- Get the source code, either
- In your checkout or extracted copy of the code there will be a 'win32' folder. Open win32\VS2015\opus.sln in Visual Studio and build it. You'll probably have to click through a few dialogs to upgrade the project build tools to the version you're using, but that's a good thing to do. You may need both debug and release builds depending on what you're making.
You'll now have .libs in the Opus source checkout in win32\VS2015\Win32\Debug and \Release that you can use in your project. (You could also add the Opus project into your solution and make your SIP project depend on it.) You'll need to add the paths to these folders to your project linker settings.