How to use data objects in BPMN?

In order to use data objects in BPMN firstly, you have to understand the syntax and meaning of every object type.
There are eight elements representing data in BPMN specification:

Data Object – a Data Object represents information flowing through the process, such as business documents, e-mails, or letters

Data Input – is an external input for the entire process. A kind of input parameter.

Data Output – is the data result of the entire process. A kind of output parameter.

Collection of Data Object – represents a collection of information, e.g., a list of order items

Data Input Collection – represents a data input collection of information, e.g., a list of stock items

Data Output Collection – represents a data output collection of information, e.g., a list of stock items

Association – a data association is used to associate data elements to Activities, Processes and Global Tasks

Data Store – is a place where the process can read or write data, e.g., a database or a filing cabinet. It persists beyond the lifetime of the process instance.

Initiating Message – an initialing message represents an item that is transferred, manipulated, or stored during the process.

Non-Initiating Message – a non-initialing message represents an item that is transferred, manipulated, or stored during the process. The filled icon represents a non-initiating message (or a message which a participant has sent in response to a previous message it received)