Hello
Refer to Blogs below for reference
Part 3 : Creation of a workflow, standard task and binding of Rule
How to Create and Trigger Class Based Workflow from Web Dynpro ABAP - Part 1
How to Create and Trigger Class Based Workflow from Web Dynpro ABAP - Part 2
Raising ABAP OO events for workflow - ABAP Development - SCN Wiki
How to Create and Trigger Class Based Workflow from Web Dynpro ABAP - Part 4
Regards
sandy