In any activity in which a context reference refers to a repeating element of the .xsd, you can select which element or elements you want to reference in your target schema by setting index properties in the Set Context References dialog box.
For example, you must set the source context references for an Assign activity that has repeating elements, and then set the index to choose the first element, last element, a literal value, or an integer as the context reference.
To set context references for repeating elements:
In the Business Process Editor, select the activity or resource in your project to which you want to set the context reference.
Select Window>Show View>Properties from the menu bar.
In the Properties
View, click 
in
the Value column of the Source or Target Context Reference field.
In the Set Context References dialog box, select a context variable to reference the context. Example
In the Content Model display, navigate the tree from root node down to the repeating element.
Right-click on the repeating element to display a Set Index shortcut menu, and choose one of the following:
Set index to choose first element.
Set index to choose last element.
Set index to choose the context reference as an integer. For example, set to 'n' where n is defined as an Integer context variable.
Set index to a literal value, for example, 3.
Note: When setting literal values, note that the Business Process and Map Editor are one-based and the Rule Set Editor is zero-based.
Click OK to save your changes and close the dialog box.