The basic steps would be:
1) Change the citrix server to install mode
2) Install P6 Client as per normal
3) Change the citrix server to user mode
4) Apply minimum file/folder permissions
5) Move the pm.ini file to the users home folder (or default folder) and rename the original pm.ini file so it does not get used
6) Publish the app via Citrix.
For the change mode you will need to:
1) Start a command prompt window (with admin rights)
2) Run "change user /install"
Do any installations
3) Start command prompt window (if you closed it)
4) Run "change user /execute"
In regards to the permissions I would recommend following the Oracle article: 895873.1
But the main things to do is read/write permissions to the following folders (locations may vary slighly depending on the version you have installed)
C:\Program Files\Common Files\Primavera Common
C:\Program Files\Oracle\Primavera\Primavera P6\
*Go for the Program Files (x86) folder if you are using 64bit.
You can go lower down and set the permissions for certain folders and files but I tend to just go for those two high level folders to make life a little easier.