The process is a bit different whether you are running on cloud or server, but this has been discussed several times here on Answers - here is one of the most recent threads. First you need to merge the project configuration using a tool like Configuration Manager for JIRA and the use the JIRA project importer to import all the data. Check-out Configuration Manager's documentation for more details on moving projects between instances.
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG