Please follow below given steps to add SPF record for the domain from the client area.
1. Login to the client area at the URL https://clients.domaincentral.com.au
2. Click on Domains tab >> Manage DNS
3.To edit the DNS zone please click on pencil icon in front of the domain name.
4. Click on Add Record button, here you need to select DNS record Type TXT.
5. Enter the domain name and make sure to add dot (.) at the end of the domain name. Note: dot (.) need to add in name field while adding new records for domain.
6. Update TTL value 3600 or as per your requirement.
7. Enter the SPF data in RDATA field and save changes.