First, please make sure that Iterations are enabled in your Workspace.
You can bulk add, remove, or re-assign Stories to an Iteration anywhere you can edit multiple Stories (see section for Bulk Editing Stories). This includes the Stories, Epic, Label, Dashboard, and Search pages. In addition, when you are on an Iteration detail page or the general Iterations page, you can perform a bulk update for Stories that need to be moved to a different Iteration by selecting multiple Story cards.
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