Need to add SPF record

We are adding a new service to our website and in order for it to be able to send/receive emails I've been told that we must add and SPF record, specifically:

• SPF Record Change: Your domain name Registrar holds your DNS and other records. This is where the change must be made: on the domain name registrar's page (Go Daddy, Network Solutions, eCatholic, etc.)
• Someone with access to your Domain Registrar would have to log in, create or edit one, and place the following in the SPF record: include:spf.massintentions.com ~all

Can you help or give me directions?