You can purchase a tent, as well as camping equipment (mattress, sleeping bag, etc.) beforehand or at DreamVille.
Beforehand you can purchase a tent and camping equipment with the Magnificent Greens Tent Package. This package includes a unique limited edition Tomorrowland DIY tent that you can pitch at the Magnificent Greens Area. You can also purchase a (Spectacular) Easy Tent Package, which includes a pre-pitched limited edition Easy Tent that you can take home after the festival. These DreamVille Packages are available during the ticket sales and you can find more information on them on the DreamVille website.
You can also rent a CAMP2CAMP tent or buy a Magnificent Greens DIY Tent during the Add-On Sale (online sale before the start of the festival). More information and prices will become available closer to the festival.
You can also buy a tent or camping gear at DreamVille in the Camping Store at the Marketplace or Magnificent Greens Area.