EASY SETUP (for players who don't have any other custom keybinds for other mods)
----------
Step 1.
Copy input.xml to
<path to your game>\The Witcher 3 Wild Hunt\bin\config\r4game\user_config_matrix\pc
Overwrite the existing file.

Step 2.
Copy input.settings to
<Your Documents Folder>\The Witcher 3
Overwrite the existing file.


__________________________________________


ADVANCED SETUP (for players who have custom keybinds for one or more other mods)
--------------
Step 0.  
Find the files you are going to work with.
input.xml can be found in <path to your game>\The Witcher 3 Wild Hunt\bin\config\r4game\user_config_matrix\pc
input.settings can be found in <Your Documents Folder>\The Witcher 3
I also highly recommend downloading Notepad++ and its file comparison plug-in, if you don't already have them.


Step 1.
Open the Immersive Cam input.xml in Notepad++.
Open your existing input.xml in Notepad++.
Run a file comparison on the two files.
Copy the extra lines from the ImmersiveCam input.xml into your existing input.xml.
Save your existing input.xml.

Step 2.
Open the Immersive Cam input.settings in Notepad++ and copy/paste the text below to the top of the file.  Save the file.

[Exploration]
IK_PageDown=(Action=CamHeightDecrease)
IK_Up=(Action=CamDepthIncrease)
IK_PageUp=(Action=CamHeightIncrease)
IK_End=(Action=CamReset)
IK_Insert=(Action=CamSet)
IK_Left=(Action=CamOffsetDecrease)
IK_Right=(Action=CamOffsetIncrease)
IK_Down=(Action=CamDepthDecrease)

[Horse]
IK_PageDown=(Action=CamHeightDecrease)
IK_Up=(Action=CamDepthIncrease)
IK_PageUp=(Action=CamHeightIncrease)
IK_End=(Action=CamReset)
IK_Insert=(Action=CamSet)
IK_Left=(Action=CamOffsetDecrease)
IK_Right=(Action=CamOffsetIncrease)
IK_Down=(Action=CamDepthDecrease)

[Swimming]
IK_PageDown=(Action=CamHeightDecrease)
IK_Up=(Action=CamDepthIncrease)
IK_PageUp=(Action=CamHeightIncrease)
IK_End=(Action=CamReset)
IK_Insert=(Action=CamSet)
IK_Left=(Action=CamOffsetDecrease)
IK_Right=(Action=CamOffsetIncrease)
IK_Down=(Action=CamDepthDecrease)

[Combat]
IK_PageDown=(Action=CamHeightDecrease)
IK_Up=(Action=CamDepthIncrease)
IK_PageUp=(Action=CamHeightIncrease)
IK_End=(Action=CamReset)
IK_Insert=(Action=CamSet)
IK_Left=(Action=CamOffsetDecrease)
IK_Right=(Action=CamOffsetIncrease)
IK_Down=(Action=CamDepthDecrease)

[Diving]
IK_PageDown=(Action=CamHeightDecrease)
IK_Up=(Action=CamDepthIncrease)
IK_PageUp=(Action=CamHeightIncrease)
IK_End=(Action=CamReset)
IK_Insert=(Action=CamSet)
IK_Left=(Action=CamOffsetDecrease)
IK_Right=(Action=CamOffsetIncrease)
IK_Down=(Action=CamDepthDecrease)