How to set value to custom attribute.

Hi all,
I want to set value to custom attribute "count" whose attribute type is integer for defect type of work item using API.
I added custom attribute named "count" to defect type of work item using process configuration tab of project area.
Process configuration-->Project Configuration-->Configuration Data-->Work Items--> Types and attributes.
I want to set its value to some hard coded value say 1,  programmatically using API.
For this, should I access project area first then work item and then attribute for particular type of work item or I can directly set value to required custom attribute.?
Please tell me a way to do this


Thank You