Connect 5v 30a relay with Arduino Uno
From the Amazon page you linked to: 


  1 dc+ : Dc power supply positive pole
  2 dc- :Dc power supply negative pole (i.e. ground)


Arduino:
VCC: positive DC power supply
GND: ground

technically, VCC = the voltage at the collector of a transistor, these days it's used as shorthand for the positive output pin of an IC.