1. Copy HydraPlugin.dlr to "C:/Program Files/Autodesk/3ds Max 2013/plugins" (or other place where your 3ds max installed)
2. Create folder "C:/[Hydra]/pluginFiles/”

or

Run install.bat with administrator privilegies (!) from command prompt (!)
For now, the plugin and server are avaiable only as 64 bit applications, sorry.