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.
I have multiple projects that use variations of the same base workflow. The variations depend on the requirements of the project or issue type. The variations mostly come in the form of new statuses ...
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