There's probably a release inside the car. Look around the driver's seat, or on the dashboard. You should be able to download the owners manual for the car. It may be different for different model years.
The gas tank on the 2004 Hyundai Santa-FE holds 19 gal..
The gas tank on the 2012 Hyundai Santa-FE holds 18.0 gal..
The gas tank on the 2003 Hyundai Santa-FE holds 17.2 gal..
The gas tank on the 2014 Hyundai Santa-FE holds 18.8 gal..
The gas tank on the 2013 Hyundai Santa-FE holds 17.4 gal..
The gas tank on the 2002 Hyundai Santa-FE holds 17.2 gal..
The gas tank on the 2009 Hyundai Santa-FE holds 19.8 gal..
The gas tank on the 2011 Hyundai Santa-FE holds 18.0 gal..
The gas tank on the 2006 Hyundai Santa-FE holds 19 gal..
The gas tank on the 2005 Hyundai Santa-FE holds 19 gal..
The gas tank on the 2008 Hyundai Santa-FE holds 19.8 gal..
The gas tank on the 2007 Hyundai Santa-FE holds 19.8 gal..