To achieve arrancar state you must first have 100ZE.
Then you can submit a fanciction or an appropriate thread/post that shows your journey to becoming an arrancar. It will be looked over by admin and approved/disapproved acordingly.
Once you have achieved Arrancar state you must Post in this forum, using the template and describe you appearance and abilities. Once this has been checked over by admin it will updated in your bio.
Many thanks.
Xavier Cranwell.