Well, technically you can't, Microsoft.Web.Administration only comes with an OS (like Windows Vista / 2008 or Windows 7 / 2008R2). You can conceptually be able to refer to it if you copy the DLL and can compile, but you cannot even run the application to manage remote servers, since MWA requires that other objects be locally available for work, namely, a COM library that actually implements IIS configuration system.
You need to hack a little attempt to make it work, since you will need libraries like DCOM (ahadmin), but even if you earn it, the solution will still be considered unsupported.