You may use cURL, Postman REST Client or any other REST API client to perform the Update Issue PUT request. For all our Jira  Data Center / Server REST API go to Atlassian Developer REST APIs

Using cURL

1. Send cURL command as follows:

   curl -v -u username:password -X PUT -H "Content-Type: application/json" --data @"/Users/admin/work/atlassian-support/workshops/epiclink.json" http://localhost:6310/j6310/rest/api/2/issue/10141

2. Example of JSON data

   {
       "fields": {
          "customfield_10006": "SSP-24"
          }
   }

Using Postman REST client

例: