To answer your question, in order for someone on the Candidate Register to make such a change, the normal procedure is to either submit a description of the previous training and experience that you believe has prepared you for assessment and which populations, or a learning plan that can be included as part of your supervision. Please review the section “Candidates Wishing to Expand Within Their Area of Practice” in the Supervision Handbook.
If approved, you would also need to ensure supervision related to your work with assessment and to add goals relevant to assessment to your current supervision goals.
In summary, you may submit either a learning plan or a description of your training and experience with assessment for the NSRP to consider.