Use an instance method from WF with instance reference

Hi experts.

I'm implementing a custom WF, using a Z class, so, I implemented FIND_BY_LPOR and LPOR methods. My class instance is alredy created, but I can't modify any non-key attribute, I mean, my constructor is something like this:

**This is my static method

METHOD zme_politic_constructor.

   CREATE OBJECT politic

     EXPORTING

       i_vbeln = i_vbeln.

** from this point, there are no changes in my instance attributes

   politic->zme_politic_get_marg( ).

   politic->zme_politic_id_difer( ).

   politic->zme_politic_escala( ).

   politic->zme_politica_get_authorizers( ).

ENDMETHOD.

METHOD constructor.

   me->vbeln = i_vbeln.

   m_lpor-instid = i_vbeln.

   m_lpor-catid  = 'CL'.

   m_lpor-typeid = 'ZCL_FLUJO_WF'.

ENDMETHOD.

I don't know what to do in order to modify any other attribute. Do you have any ideas?

Best regards!