Select object you want to apply modifier, then add array component. (Modifiers->Array->[Type]).

General Settings

• Type: Type of array
• Count: Size of array
• Dimensions: Dimension array
• Components changed: Update array when components of original object changed

Linear

• Constant:
  • Offset: Offset of clones in array in units of Unity
  • Rotate: Rotation of clones in world space
  • Scale: Scale of clones in world units
• Relative:
  • Object: Base object for calculate the displacement / rotation / scaling
  • Offset: Offset of clones in array in units of Object
  • Rotate: Rotation of clones in Object space
  • Scale: Scale of clones in Object units

Circle

• Radius: Circle radius
• Direction radius: Direction of radius (from original object to center of circle)
• Rotation axis: Axis around which build circle
• Use rotation: use rotation for clones

Curve

• Curve color: Color of curve
• Distance: Distance between clones
• Allow count: Uniform distribution of objects along the entire length

Object

• Object: Transform used for create the array
• Use offset/rotation/scale: Use offset/rotation/scale for clones