Wipe down the dryer thoroughly with a soft rag dipped in a disinfectant solution and rinse with warm water. Use a dry rag to dry off any remaining moisture and remove any possible mold buildup. Pay particular attention to the electrical cord so that no moisture remains on it and that it is in good condition. Spray any visible mold with a solution of warm water and white vinegar in a half-and-half solution from a spray bottle.
Plug in the dryer and see if the display is responding. Any previous settings on the dryer will have already been restored to default from being unplugged for so long. Reprogram any settings you need into the dryer.
Run the dryer with some towels or clothing as a test run to ensure the dryer is fully reset and working properly.