There are a number of different approaches to this depending on whether you want to do a one-time import or retain a link between the content in MS Project and JIRA.
If all you want is to import once and stop updating MS Project then the easiest approach is to create a CSV file as explained here. https://confluence.atlassian.com/jira/importing-data-from-csv-185729516.html
However, if you want to retain a link then you need to consider a plugin. Here are some options.
There are other options that you may also want to research depending upon your exact requirements.
Statuspage customers logged more than 194 years of collective incidents in 2018. That’s a whopping 87% increase from the 104 years logged in 2017 , and we aren’t even through December yet....
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