You need to add at least one category to the calendar before adding events.
To add categories to the calendar - choose 'Components' and select 'Events' from the drop down menu, and 'Manage Categories' from the secondary menu. Click 'New' on the right hand side.

Each calendar category should have its own distinctive color. Click on 'Color Picker' to choose a color. Provide a Category Title and a Category Name. They can be the same, but keep in mind that the Category Title should be short, because it appears in menus, while the Category Name can be longer, if you prefer. You have the option of selecting an image to associate with this category. A 'Services' category, for example, might have an image of Shabbat candles. You are not required to select an image. You have the option of entering a description of the category, but it is not required. Click 'Save' when you are done. You will now see a list of your current categories.
IMPORTANT:You must click on the icon in the 'published' column if it is red. The published icon should  be a green check mark, for the category to be active. If the icon is red, clicking on it will change it to green, and the page will reload.