Go to your Asset Store to delete an Asset from your PebblePad:

Select the Asset(s) you wish to delete by clicking the icon to the left of an Asset. These behave like tick boxes and will show a tick once selected. You can select one or many Assets to Delete. 

Click on the Icon to the right of the asset. 

Click on the 'I want to...' button that appears and Click 'Delete':

This will move the Asset to the 'Deleted' store, which can be accessed along the top of your Asset Store. You can access your Deleted Store area to Restore or Purge (permanently delete) Assets at a later time.

PLEASE NOTE: If you have more than 50 items in your Deleted Store, the oldest Assets will automatically be purged.