1. Download, install, and set up the CUDA toolkit from https://developer.nvidia.com/cuda-downloads. OS-specific setup instructions are available at the NVIDIA CUDA official website. 
2. Configure the GPU for Spark distributed training by adding a Maven dependency for ND4J's CUDA backend:

<dependency>
   <groupId>org.nd4j</groupId>
   <artifactId>nd4j-cuda-x.x</artifactId>
   <version>1.0.0-beta3</version>
 </dependency> 

3. Configure the CPU for Spark distributed training by adding an ND4J-native dependency:

<dependency>
    <groupId>org.nd4j</groupId>
    <artifactId>nd4j-native-platform</artifactId>
    <version>1.0.0-beta3</version>
 </dependency>