Setup & Configuration
After you've installed Unity, extract the file in the Part Tools zip to where you installed Unity.
For Example: C:\Program Files\Unity\Editor\Standard Packages\
Open Unity.
You should get a prompt box with 2 tabs. If not, go to File > New Project.
Select the Create New Project tab. Select the PartTools 18.unitypackage and click Create. There will be some loading bars as it prepares the project.
On the bottom left, there is a [Project] tab with a list of some folders.
This is the file explorer for your project. To the right of that in the bottom center, is the area where you will see file listings of what is contained in each folder.
Right click the Assets folder then go to Create > New Folder. Name this folder whatever you want. This will be the folder you will drag and drop model and texture files into. It's best to have a separate folder for each mod you'll be making.
Now go to the Plugins > KSP folder.
In it there is a file named PartTools. This contains the script that allows you to export models and textures from Unity to KSP properly. But we will cover the usage of that later.
Create a New Gameobject, either by going to the top menu bar; GameObject > Create Empty, or pressing ctrl+shift+N.
This will create a new object in the [Hierarchy] panel on the top left of Unity. Rename this object "PartTools" for simplicity sake.
Drag the Part Tools file into the [Hierarchy] panel on the upper left, drop it into the GameObject you just created and renamed.
Now That all of these steps have been completed, Unity is completely setup for KSP. This would be a good time to save the project. Go toFile > Save Project.

Getting Started
Open the folder you created in the Assets folder earlier. Drag and drop your model, .mtl (if applicable) and texture files into the bottom center panel (or directly on the folder).
You should now see your model and textures in the file listing, along with a folder named Materials.
Select your model from the list then drag and drop it anywhere in the [Hierarchy] panel.
The model will now show listed under your Main Camera and be visible in the center window named [Scene]. There will be an arrow triangle next to the name.
This can be clicked and will show a named listing of the individual parts of your model, and selecting any of them will automatically select that specific part of the model for working with. Alternatively, you can select individual parts or groups of a model visually from the display in the [Scene] panel in the middle center of Unity.
There is a panel on the right side of Unity called the [Inspector] panel.
Any file or part you have selected, either from the [Hierarchy] or [Project] panels, will show options in the [Inspector] panel. These options are referred to as Components.

Import Settings
Select the model from the [Project] panel's file explorer. This will reveal the Import Settings options for your model in the [Inspector]panel.
Set Scale factor to 0.1 or 1.0. This setting depends on the scaling and sizing of your model when you exported from your modeling program. 0.1 is considered default.
Check Generate colliders and Generate Lightmap UVs.
APPLY the settings.
There are other options here, but we will not cover them. Not all of these options are necessary or the values can be changed, but it's best to keep them this way by default. You will have to apply these settings to every new model you import.

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