You sure can!
To add previously uploaded music to new services, simply click "Add to more stores" on your album dashboard page.
Once you have clicked this, you will be prompted with a list of services that your music is not on from previous distribution.
Feel free to select the services you wish for distribution, and click "add."
Note: We are not able to add your work to Apple/iTunes after your work has been submitted, if you did not include Apple/iTunes in your original submission at this time. To add Apple/iTunes, you will need to create a second upload for only those two platforms, or delete and re-upload your work to all stores, including Apple/iTunes.