Jira has a common wizard interface for all the different issue tracker importers. While each importer is unique in its own way, they all follow the same basic steps, as described in the following list:

• Configuring the target data source: This step is where the target issue tracker's data is retrieved. It can be direct database access in the case of Bugzilla or it can be over the internet in the case of Bitbucket.
• Selecting a project to import to: This is where we have to choose the issues that are to be imported to either an existing project or a new project.
• Mapping the target system's fields to Jira fields: This is where the target issue maps the tracker's fields to the corresponding Jira fields. Custom fields can be automatically created as part of the process.
• Mapping a target system's field values to Jira field values: This maps the field data based on the previous field mappings. It is usually required for selecting list-based fields, such as priority, issue status, and custom fields.
• Mapping the issue link types: This step is optional depending on whether the target issue tracker supports linking. If it does, those link types will need to be mapped to the Jira issue link types.

Although the Jira importer is able to handle most instances where the data mapping is straightforward, for bigger instances with complex mapping requirements, such as project merging and conditional mapping, it is recommended that you engage an Atlassian Expert (https://www.atlassian.com/resources/experts) to handle the migration rather than relying on the importer alone.