Creating a Function 
You create a function by assigning it an ID, describing it, and by defining its attributes.
Procedure
Choose
Setup 
Access Rule Maintenance Functions 
.Choose Create.
The Function: New screen appears.
Enter the basic attributes of the function.
In the Function ID field, enter the 8-character code for the function.
Most enterprises choose a naming convention for this code. Access Control assigns default functions a four-character code.
In the Description field, enter a plain-text description of the function.
You use this description to identify the function in the interface.
From the Business Process dropdown list, select the business process to which this function belongs.
The Business Process field is a required field. It is highly recommended that you associate each function with its proper business process unless the function belongs to more than one process.
From the Analysis Scope dropdown list, select either Single System or Cross System.
Choose Single System if the function applies to one enterprise platform (SAP or non-SAP system).
Choose Cross System if the function applies to multiple enterprise platforms (SAP and non-SAP systems).
You can associate the function with an action or a permission. Use the Action list to associate an action with a function, to add an action to the list, or to delete an action from the list.
(Optional) Click the Permissions tab.
The Permissions screen appears, displaying the permissions (authorization objects) for all of the actions that have been added to the function.
CautionThis screen allows you to further restrict the access defined in the permission object. You cannot expand the access or reconfigure the permission object.
End of the caution.To modify access restrictions:
If you do not need to modify an associated permission, use the Permission Definition dialog.
To view and evaluate the details of a permission before you modify it, use the Permissions tab to expand and view each permission.
Choose Save.