If you want to hide products from your view, in most cases it's preferable to set products to Inactive rather than deleting them. Deleted products will be created again if they happen to show up in a future order import whereas inactive products will remain out of sight on the inactive list.
If you know the product will not be found in future order imports it's fine to delete it from GroovePacker. To delete a product, you'll need to change it to "inactive" first. Once they are in the inactive list, select the products you wish to delete and you'll find the delete option in the edit drop-down in the Inactive list view.
Please note that when a product is deleted it is removed from any orders it is present in. You'll see a notification of this if you open orders that contained items that were deleted.