Installation and Usage
Adding the Asset to your project
Before you start, make sure you have Poiyomi shader and VRCFury (via creator companion, ALCOM or as package) added to your project.
Also, this asset requires the VRC SDK version 3.10.3 or higher since it is using the raycast component.
If you get this warning in the Inspector when clicking on one of the prefabs:

You need to update the SDK. Creating a backup before updating is recommended - just in case. The creator compaion as well as ALCOM can update and create a backup for you.
Add the package to your project by dragging the "Crime Scene vx.x.xx.xx" from your downloads into the Project window and click on Import.

Add to Avatar
After adding the package, the prefab will be located under
Assets->Kokos->AvatarAssets->Crime Scene->PREFAB->Full or Opti.
You can now drag and drop either the full or the optimized prefab version directly onto your avatar. The difference between the two is that the optimized version lacks lights, the outline effect and the audio. Everything else is identical. For this tutorial, I will be using the full version.

Position/Scale the Scene
Since you can position the asset by using the raycast in-game. There is no need to change the default location.
If you want to scale the prefab, you need to adjust a few things.
Inside the prefab hierarchy you can find the container object. Resize it as you need.

If you are using the opti version you can skip to Align Anchor points
Next, you need to enable the Extras and the Cam game objects in the hierarchy.

Then, click on the Camera object. In the Inspector you need to adjust the Size and Far values with the same factor as you resized the Container. In my case, I scaled the Container by x0.5. So the Size has bo go from 0.9 to 0.45 and the Far value from 2.05 to 1.025.

You can test, if everything works by adding the Default layer to the Culling Mask of the camera.

If it looks like this, everything should be fine.

If you can see something like this however, try lowering the Far value untill the issue dissapears.

Align Anchor points
In this step you need to position the Left_Anchor, Right_Anchor and Head_Anchor to your avatar. To do so select each anchor in the hierarchy and position it accordingly.

Notice, that if you are in VR you can position the asset by pointing your hand in the direction and then enabling the Place Scene option in the ring menu to lock it in place. On Desktop you have to look in the direction and then the menu option.
Change Menu Location
If you want the asset’s menu to be added to one specific menu of your avatar (like an Extras menu), just select the prefab you added to your avatar in the project file browser. In the inspector, look at the 'Full Controller' component. There you can type the name of your target menu (e.g. 'Extras') into the Prefix field in the menu section.

Cleanup
When you are done with the setup, you can disable the Crime Scene Mesh in the hierarchy
Usage

Activate the scene with the Toggle Crime Szene option.
This will show the model and let you place it by using your right/left hand in VR or by looking around on Desktop.
Lock the scene inposition with the Lock Scene in place option.
Ground offset lets you lift scene to prevent clipping with for example carpets since they usually do not have collision.
The Evidences menu lets you de/activate individual set pieces.
The full version offers the Effects menu.
Here you can de/enable the flshing lights, sound and outlines.
For the outlines you need to activate them, then have a player or yourself pose inside the scene.
When you are happy with the pose, enable the Freeze Outlines option which freezes them in place.