In order to set your store on vacation mode please log into your dashboard. You will see on the left hand side a gray column with several options. One of those options is Settings. Click on this option which automatically brings you to your store information. If you scroll down the page right after your address field you will see Go to Vacation. Click on the box and you will see you then have 2 options of what closing style you prefer. You can either instantly close or chose a date range. Once you decide this you are able to set a vacation message. When this information is complete scroll to the bottom of the page and make sure to "Update Settings"
Your store will then be closed from the public.
*Just remember once you are ready to be live again you MUST go back to the same section and unclick the box and save.*