First thing to do is to go to https://www.google.com/calendar/render or just google “google calendar”.
If you are logged in your Google account, you should see a small calendar on the left side and the main UI in the center.
Click on the “month” tab.
An example: you want to create an alert for 20 March 2014. Click on the box that says 20 March > edit event > name your event, add a description > save.
You will receive on 20 March, an e-mail with the title and description from your alert.
If you want to receive repeated alerts, when editing your alert, click on the “repeat” checkbox.
If you want to create an alert for June 2014, browse for June in the small calendar from the left side and click on any date so the main window will get updated.