If you are flying to the conference, the airport is Greenville-Spartanburg (GSP).
Please note that the conference is in Greenville, South Carolina, NOT Greenville, North Carolina. Some people are confused about the distinction between South Carolina and North Carolina. They are different states, different states of mind, and located in different places: as the names indicate, South Carolina is closer to the Equator, while North Carolina is closer to the Arctic.
There is a free shuttle between the conference hotel and GSP airport. But you will need to call them in advance to make a reservation. Their phone number and schedule can be found here. During off hours you can take a cab or an Uber or Lyft for $30-ish.
If you are driving to the conference, click here for directions. Hotel parking is only $7.50 per day.
To save money on flights, you might consider flying into Asheville (AVL), Charlotte (CLT), or Atlanta (ATL) and renting a car there. Depending on traffic, downtown Greenville is 1 hour from AVL, 1.5 hours from CLT, and 2.5 hours from ATL.