vAT exempted & quarterly returns for secondary occupation

I started my business this year. When I started up, Securex advised me that it would be best to work with quarterly returns. So I had this activated. I am VAT exempted and therefore do not charge VAT to my customers. Do I need to indicate in Dexxter that I am not subject to VAT and still submit quarterly returns, or do I need to charge my customers 21% VAT and set myself as subject to VAT on Dexxter?