You can attach a learning path to the portal directly from the learning path edit page.
1. Press Communities
2. Press the Add button
3. Select the portals where you want to add the learning path and press Add.
4. The learning path has now been added to the selected portals and you can go back by pressing the "Back" button.
The top path is added to the last one in the portal. If you want to change the order of the learning paths, do so in the Community section. See the instructions here.