The next step after completing the VCU108 Quick Start Guide is to connect the loopback boards & cables provided in the VCU108 kit and test the external board interfaces. Once you have all the loopback boards and cables attached, you will run the Board Interface Test located in the Documentation and Design tab of the VCU108 product page.
Once you have completed the Board Interface Test explore other Design Examples located in the Documentation and Design tab of the VCU108 product page.
Now it's time to create your own target design using the Vivado Design Tools.