Much of the time you would trigger a web dynpro plug by creating a new action and assigning a plug to it. When doing this the ABAP code which performs the trigger is inserted into the actions method automatically, see trigger abap webdynpro plugs for more details. You can add the abap code which triggers a views outboud plug into any section of code within the web dynpro view, the code required to do this can be found below.
If your Plug Name is LOGOUT_OUT then the plug trigger code is as follows: wd_this->fire_LOGOUT_OUT_plg( ).