You will be invited to the first assessment event which falls after the completion of your unit (key dates here). You will receive your invitation between the 'Unit completed by' and the 'Invitation to event by' date, per the Assessment Schedule linked above. With your invite, you will be sent a GDrive folder in which to upload your work (unless you are a Music student, in which case you will submit via OCA Learn).
Please see the Assessment Guidance on OCA Learn for any other assessment queries.