If you study on a programme that comes with accreditation then you should be eligible to apply for accredited status.
Please check the website of your accrediting body for full details and instructions on what is required to become accredited. In some cases they will just need to see your University of Greenwich degree certificate, but for others you may need to have worked for a certain number of years and/or show personal development - it depends on the accrediting body.
The accrediting body website will provide full details - the university is unable to grant accredited status for any programme, but if you have any questions please do speak to your Programme Leader or submit an enquiry which can be passed on.