Calculate the sum of a custom field

[Jennifer Bill]

I'm new to JIRA and not a programming/formula background.  

I have created a Custom Field to make a note of how many Deliverables we have in each epic (to suit our projects) 

How do I get a total of these in a Dashboard?  

My dashboards are currently totally the number of issues/epics assigned to areas or team members rather than totally the quantity of the custom field?  

Is there an option without having to purchase an Add-on?  

[Haran Kumar]

@Jennifer Bill , Though you mentioned that you are not a programmer , I dont find a way to do your task without involving and coding. I may be wrong but still, I would like to add some light , you may refer to the following discussion . 

https://community.atlassian.com/t5/Jira-questions/How-to-sum-data-from-customfield-using-jql-and-scriprunner/qaq-p/1063758