You can update all your existing ideas at once by using the "bulk edit" option in the ideas list page.
With this option you can add tags, user personas, products, as well as change status, state, author, and owner.
To begin the bulk editing process, click on the checkbox above the ideas list. This will allow you to highlight all ideas on the page, select your entire filtered list (if you have any filters applied,) or modify your entire backlog.
Once you have made the desired selection, a slide out will pop out allowing to make the necessary changes.
You can also bulk edit your search results by clicking on "bulk edit" on the search results page.
If you're looking to bulk upload new ideas, that is possible via a CSV upload.