Also make sure your Configuration.h file looks like mine in this section. If you don't have things like mine, you won't be able to home in the center of the bed:
Code:
// @section homing


// The center of the bed is at (X=0, Y=0)
//#define BED_CENTER_AT_0_0


// Manually set the home position. Leave these undefined for automatic settings.
// For DELTA this is the top-center of the Cartesian print volume.
//#define MANUAL_X_HOME_POS 100
//#define MANUAL_Y_HOME_POS 100
//#define MANUAL_Z_HOME_POS 20


// Use "Z Safe Homing" to avoid homing with a Z probe outside the bed area.
//
// With this feature enabled:
//
// - Allow Z homing only after X and Y homing AND stepper drivers still enabled.
// - If stepper drivers time out, it will need X and Y homing again before Z homing.
// - Move the Z probe (or nozzle) to a defined XY point before Z Homing when homing all axes (G28).
// - Prevent Z homing when the Z probe is outside bed area.
#define Z_SAFE_HOMING


#if ENABLED(Z_SAFE_HOMING)
  #define Z_SAFE_HOMING_X_POINT ((X_MIN_POS + X_MAX_POS) / 2)    // X point for Z homing when homing all axis (G28).
  #define Z_SAFE_HOMING_Y_POINT ((Y_MIN_POS + Y_MAX_POS) / 2)    // Y point for Z homing when homing all axis (G28).
#endif