Adding issues from Structure Board
You can also add issues from another structure. Simply open the structure in the secondary panel, and use drag-and-drop or copy/paste to import issues.
Adding issues from the Issue Page
You can also add issues to a structure directly from their issue page.
From the issue page, select the structure you want to add the issue to, highlight the place you would like to insert the image (it is inserted immediately after the highlighted line) and click the Paste button.