You need to open the command prompt which comes with VS.
You need to use the gacutil tool
gacutil /i myown.dll
For more info:
http://msdn.microsoft.com/en-us/library/ex0ss12c%28v=vs.80%29.aspx
You can refer this page for doing so programmatically:
You can otherwise use Microsoft Windows Installer for deploying your application :
http://codefornothing.wordpress.com/2007/11/27/short-msi-tutorial/
And you can find the MSI here, if need be.
http://www.microsoft.com/en-in/download/details.aspx?id=25#overview