Trigger: On Page Load
Want a popup to show up right when the page loads? Or a few seconds later? You can do that with HollerBox.
Go into editing your popup, then you want to go to Triggers.
When you see the Edit Triggers, you will want to turn on On Page Load. If you enter 0 seconds, then the popup will show as soon as the page is loaded. If you enter any other time, then Hollerbox will wait that many seconds before showing your popup.
After you have turned on what triggers you want, you can close the Edit Triggers (top-right corner). Then save / publish your popup.