Get and update customfield values in Zephyr Scale for Jira

Hello. 

I can't figure out how i can get value of customfield in Zephyr Scale for Jira?

For example i need to get current value of customfield with id 482 and update it via rest api

I try to use this query https://jira/rest/tests/1.0/testcase/TEST-12334?fields=customfield_482 to get current value of field but no luck