Download from here:

http://www.citrix.com/English/ss/downloads/results.asp?productID=186&c1=sot2755&c2=pov1863153&c3=ost12713

Choosing which client to use (basically, if you want pass-through authentication, use the full online client, not the web one):

http://support.citrix.com/proddocs/index.jsp?topic=/online-plugin-120-windows/ica-xd-choose-client.html

To extract, install, and remove the individual plug-in .msi files (and talks about the installation order):

http://support.citrix.com/proddocs/index.jsp?topic=/online-plugin-120-windows/ica-extract-msi.html

To configure and install the online plug-in using the plug-in installer and command-line parameters:

http://support.citrix.com/proddocs/index.jsp?topic=/online-plugin-120-windows/ica-configure-command-line.html