You may want to take your website down for a few minutes or a few days while you preform maintenance, to do this you will want to put your website into Maintenance Mode.
NOTE: As long as you are signed in to your website, it will still be visible to you.
Step 1. From the Dashboard go to Settings > Maintenance Mode
Step 2. You want to tick the radio button Activate.
a) You can also specify a time that you would like your website to deactivate out of Maintenance Mode.
Step 3. Click Save.