[TUTORIAL] Using Assimp with Unreal Engine

It means that if you’re using a “blueprint only” project, you have to turn it into a “C++” project. Then, the “Build.cs” files will appear in the following path:
<PathToYourProjectDirectory>/Source/<NameOfYourProject>/

If your project is called “HelloProject” then the path to the Build.cs will look like this:
<PathToYourProjectDirectory>/Source/HelloProject/HelloProject.Build.cs