How can I get a scripted field to show the sum of story points per user per sprint?

[Tae Hee Lee]

I'm using the MISC CUSTOM FIELD to create a groovy script to show a value in the custom field the sum of the story points for the selected user of the selected sprint. 

I'm just starting to get to know the groovy script, but I have no idea which of JIRA assemblies I have to import, or how to write the script to get the expected result. 

Can anyone help me out on this problem? Please.