Assigning context object to field

Hello All,

I have created the context object in IR. Now want to assign this to one field. Where should i assign this.

I have gone through sap.help, but i am not able to get the exact place,

"To assign the context object to a request message field, enter it in the Context Object column by using the input help. For message interfaces, the structure of the request message is displayed on the Context Object tab page."

Where is the Context object Column exactly? Please help me.

Thanks for all your help in advance.

Sidd.