OpenTK does not come with any installer or setup. Instead, you download the OpenTK binaries and add a reference to "OpenTK.dll" in your Visual Studio/SharpDevelop/MonoDevelop project. (Unzip the binaries first!)
To run all of the OpenTK builtin examples, the following software is required:
This is also the software required for an end-user running an OpenTK application. Note that OpenAL is not strictly required if the application does not use any sound.
If you want to start developing applications using OpenTK, first make sure the items under "OpenTK demo" are installed, then download a compiler/IDE for .NET/mono. Here are some popular choices:
Setting up an OpenTK application in Visual Studio Express
It is a good idea to add "OpenTK.dll.config" to your project, and make sure the "Copy To Output Folder" (not "compile"!) is set to "Copy Always". The application will run without this on Windows, but not on Linux or Mac OS X.
Last, but not least, make sure the "Copy Local" property is set to true for the OpenTK reference, to simplify the distribution of your application.
Setting up an OpenTK application in SharpDevelop
Include the "OpenTK.dll.config" in your project, if you want it to run under Linux Mac OS X.