This first-time user guide provides introductory material to Drift Diffusion Lab on nanoHUB. It includes a tour of the Rappture interface, which notes key inputs and typical outputs. It also provides an introduction to concepts of drift and diffusion in a semiconductor. We discuss the default simulation (What happens if you don't change any inputs, and just hit "Simulate"?) as well as the limitations of the tool. We conclude with several references for further study.