Aspen is fairly walkable and also has a great public transportation system (RFTA). RFTA is free within the towns of Aspen and Snowmass. Buses are no more than 15 minutes apart beginning at 6:30 AM-12 AM. Please find bus schedules here. The schedule for Snowmass Village to Buttermilk Mountain (the venue) can be found here. Snowmass Village has its own shuttle service to get around Snowmass Village which can be found here.
Another option is the local taxi service. High Mountain Taxi runs 24 hours a day and can be booked in advance. More information here.
Uber and Lyft are also an option but wait times can be slightly longer than usual so plan ahead.
There is ample parking available at the venue. If you choose to Uber/Lyft home from the event, you are able to leave your car overnight and pickup by 10am the next day.