It took a day or two after I put the tracking code on each of my pages for the status on my Google Analytics Tracking Info tab to be updated from "Tracking Not Installed" to "Universal Analytics is enabled for this property". During this time I was seeing regular activity in my tracking reports.

If you're brand new to Google Analytics, the default reports only include data up to the previous day. If you want to check for activity on the same day that you added the tracking code, you have to adjust the date range to include the current day's activity.