1. Place the jar on the main unit with the lid on top. Align the 'blend' icon on the jar with the 'unlocked' icon on the main unit.
2. Turn the jar clockwise until it is locked securely into the main unit. Make sure you turn the jar clockwise all the way until the 'blend' icon on the jar is aligned with the 'locked' icon on the main unit, so that the groove below the handle clicks into the locking area

See the pictures below to see how to align the icons correctly.