Hi Nazir,
using the process framework outside the standard components for the handling of utilities contracts (e.g. IUICCON) is a little tricky. Therefore, I wanted to make sure you indeed need to use this class. I wanted to write a blog on how to do this for quite some time. So maybe your question will be the trigger to finally do it 
.
If you want to see how the SAP standard uses the process classes see component IUICCON. What you need to do in you case is the following:
1. Instantiate the process manager using the contract item or header and a process profile
proc_mgr = cl_crm_iu_process_mgr=>get_instance ( item_guid = item_guid
profile_id = 'DEFAULT' ).
2. Check if the process category (in the example below 'IUMO', the category id for the process CONTRACT_START_CANCEL in the DEFAULT process profile) you want to execute is executable
is_executable = proc_mgr->is_executable( category_id = 'IUMO' ).
3. Execute the process. This will execute the process class that is customized for the process profile and category_id and return the BOL objects that need to be saved.
proc_mgr->start(
EXPORTING
category_id = 'IUMO'
IMPORTING
objects_to_be_saved = objects_to_be_saved ).
Afterwards you need to save the BOL objects using the BOL transactions.
Best,
Christian