1 stick of 8gb RAM

Hi I just got my stuff for my pc and I thought I ordered 2x4gb sticks of RAM but got one. My motherboard cant run only one stick of RAM. Can I buy another 8gb stick of RAM same model and will it work with my motherboard? Please I need your help I am a first time builder and I am a little stressed out. My motherboard is an Asrock z77 extreme4.

Yes you can.