Copying is available to paid plan users only as there's a limit of 1 CJM, 1 Impact Map, and 1 Persona per user on the free plan. So, if you're the one with a paid plan:
Go to the page of the project with the map you want to copy.
Click on the COPY icon on the right of the impact map’s bar.
Choose a target workspace and project for your map's copy and click on the COPY button.
To copy an IM together with maps and personas that are linked to it, check the box near the “Copy all linked map/personas” option before confirming the copy action. To copy an IM structure only, select the "Clear all content" option.
A copy of your impact map will appear in the workspace and project that you've selected.
That's it, folks!