Step by step manual on downloading DWSIM is available here.
Detailed information about DWSIM and its features are available here. It will give you a general idea of DWSIM's features. All the links from Downloads to Tutorials can be found on the left hand side pane. The software has an interactive Wizard-based GUI.
Spoken Tutorial & FOSSEE, IIT Bombay has created spoken tutorials for the purpose of easy learning of DWSIM. Click here to access the spoken tutorials on DWSIM.