Creating a cell prefab

First, open your mod in Unity. If you don't have a project, please visit Introduction.

Go to Assets/Cell Prefabs, Show it in Explorer, and copy-paste any prefab. Rename it to whatever you want.

Go back to Unity and double-click your prefab to open it.

In the Sprite Renderer, change sprite to the texture of your cell (from Assets/Assets/Cells).

Remove whatever cell script there already was (such as Mover), click "Add Component" and search for your script.

In your newly created component, change Cell Type to yours, and you should be done with the prefab!