Document robot setup for PolyScope X (#302)

Now that we have the External Control URCapX released, we should add
that to our setup instructions.

Author: urfeex

doc/images/initial_setup_images/px_01_welcome.png

@@ -205,9 +205,65 @@ application.
 
    .. group-tab:: PolyScope X
 
+      The latest release can be downloaded from `GitHub (URCapX)
+      <https://github.com/UniversalRobots/Universal_Robots_ExternalControl_URCapX/releases>`_.
+
+      To install it you first have to copy it to a USB stick and plug that into the robot's teach
+      pendant.
+
+      On the welcome screen click on the hamburger menu in the top-left corner and select *System
+      Manager* to enter the robot's setup.  There select *URCaps* to enter the URCaps installation
+      screen. You'll have to press *unlock* and enter the admin password to be able to install new
+      URCaps.
+
+
+      .. image:: ../images/initial_setup_images/px_01_welcome.png
+         :target: initial_setup_images/px_01_welcome.png
+         :alt: Welcome screen of a PolyScope X robot
+
+
+      There, click the "+URCap" button at the top-right to open the file selector. There you should see
+      all urcap files stored on a plugged USB drive.  Select and open
+      the **external-control-X.Y.Z.urcapx** file and click *Confirm*. A popup should ask you to
+      confirm the installation.
+
+      .. image:: ../images/initial_setup_images/px_05_urcaps_installed.png
+         :target: initial_setup_images/px_05_urcaps_installed.png
+         :alt: URCaps screen with installed urcaps
+
+      Upon confirmation, the external-control URCap should be listed as installed.
+
+      After the robot rebooted you should find the **External Control** URCapX on the *Application*
+      Screen. If you open it, you will get to its configuration screen.
+
+      .. image:: ../images/initial_setup_images/px_07_installation_excontrol.png
+         :target: initial_setup_images/px_07_installation_excontrol.png
+         :alt: Configuration screen of External Control URCapX
+
+
+      Here you'll have to setup the IP address of the external PC which will be running the remote
+      application. Note that the robot and the external PC have to be in the same network, ideally in a
+      direct connection with each other to minimize network disturbances. The custom port should be left
+      untouched for now.
+
+      To use the new URCaps, create a new program and insert the **External Control** program node into
+      the program tree
+
+      .. image:: ../images/initial_setup_images/px_10_prog_structure_urcaps.png
+         :target: initial_setup_images/px_10_prog_structure_urcaps.png
+         :alt: Insert the external control node
+
+
+      .. image:: ../images/initial_setup_images/px_11_program_view_excontrol.png
+         :target: initial_setup_images/px_11_program_view_excontrol.png
+         :alt: Program view of external control
+
+
+      If you select the External Control program node, you'll see a button "Update program"
+      appearing next to it. With the external application started, press it to receive the script
+      code.
+
       .. warning::
 
          Support for PolyScope X isn't fully developed, yet. Please consider using External Control
          with PolyScope X as an open beta.
-
-      For details on installing the External Control URCapX, please see https://github.com/UniversalRobots/Universal_Robots_ExternalControl_URCapX