I am very new to jira plugin development , I have jira plugin that support jira 7.2.2 . I want to upgrade that one to 7.3.2 . Please help me how to start this
It all depends on what the add-on does. Read over the Preparing for JIRA 7.3 at https://developer.atlassian.com/jiradev/latest-updates/preparing-for-jira-7-3 and see if anything there jumps out at you as something that might be applicable to what you’re doing.
Even if there isn’t anything - start a JIRA 7.3 instance and test the add-on. More than likely it will work (there are cases though where it won’t and it won’t be documented in the above url).