You can remove releases from your "manage music" page once you've logged in to your account.
On this page you will see an "Action button" under your release - click on this and then the "takedown" button at the bottom of the dropdown menu.
Record Union will send a request within24 hours for your music to be removed from all the digital services it is currently available on. Usually the music will be removed within a week but in some cases this can take as long as 4-6 weeks.
Once a takedown has been requested, it cannot be reversed and it won't be possible to get it back into stores.