You can check your site statics in two different ways: default statistics and Piwik statistics.
The default statitics are always enabled. Web site statistics will display the current month of log data. Clicking on the left menu you can navigate through different statistics and in the upper part the date range can be adjusted.
On the other hand, Piwik statistics need the Piwik module to be enabled. If it's not enabled, enable it.
If you had your module already enabled, your site statistics will be presented like the following screenshot. You can set a range for the stats as well.