Call up your local centre and get booked in for the needs assessment. Once you have had the assessment the assessor will draw up a report stating what you need. The report then gets sent to student finance (you have the option to view and approve the report prior to this if you wish) to be approved and then you can go about getting your stuff delivered.
It is all very friendly and the assessment is a chat / discussion about your prior experiences and needs. (ie. what you find difficult, what you think may help, what they can offer, etc). Probably takes about 2 hours and it is nothing to worry about.