To add new data source to the calendar, use “Create New Source” link.

Type the name of new data source and check the box “Show on calendar”.

Selecting Web-Site for Data Source
Select the required web-site in the dropdown.
Note: you can add lists from any amount of sites from SharePoint site collection.

Selecting List for Data Source
Then select the required list with data.

Adding Displayed Column
Select the displayed column.

Fields for Calendar Item Tooltip
Now select fields for calendar item tooltip. Selected columns with data will be displayed when clicking on the item in the calendar.

Attachments and Pictures in Calendar Item Tooltip
You can allow attachments show for items of this data source. It is also possible to adjust preview of attached pictures if required. Check appropriate boxes.
Defining date fields for calendar entries
Define date fields for calendar entries (start time and end time columns).

Adding Percent Completion
You can also display percent completion for your events. It is usually applied for lists of Tasks type. The completion status will be displayed in the Tasks view (Days or Hours). In order to adjust percent completion view, select field from which the percent value will be taken. On this step you can also define the height of percent completion bar and select appropriate color.

Then select color for the items background.
