In general, you should use the preconfigured Stylus Profiles. But if you want to adapt the Stylus Profile manually to adjust it to your needs, then this guide is for you. Or if you have already customized profiles and want to merge the Stylus Profile into the exisiting one.
First select the MixedRealityToolkit GameObject in your scene and navigate to the Input Section
Input Data Providers -> Add Data Provider
and select the HoloLight.STK.MRTK -> StylusDeviceManager
<= MRTK 2.5.4 && <= STK 1.0.5
In the Pointers Section add 3 new Pointer Options.
Select the Controller Type to Stylus, Handeness to Any. Add the three Prefabs StylusSpherePointer, StylusRayPointer and StylusPokePointer to the Pointer Prefab field. Inside the Holo-Light/STK/MRTK/Providers/StylusInput/Pointer/ you can find there 3 prefabs.
>= STK 1.1.0
In the Pointers Section add 3 new Pointer Options.
Select the Controller Type to Generic Unity, Handeness to Both. Add the three Prefabs StylusSpherePointer, StylusRayPointer and StylusPokePointer to the Pointer Prefab field. Inside the Holo-Light/STK/MRTK/Providers/StylusInput/Pointer/ you can find there 3 prefabs.
<= MRTK 2.5.4 && <= STK 1.0.5
In the Pointers Section add 3 new Pointer Options. Add 3 new Actions and Name them Stylus Pose, Stylus Action and Stylus Back. Stylus Pose should be set to Six Dof, Action and Back to Digital. See the picture below, how it should look like.
<= MRTK 2.5.4 && <= STK 1.0.5
Then open Controller Definitions inside the Controllers section. There you will see Stylus Controller. Click on it and make sure it is configured as in the picture below.