Securing the box has two aspects to it. One is securing the lid of the storage box. There are plenty of boxes that come with locking mechanisms. But if you want to add a lock to the box you already have, then you can either fix two locking eyes on the box or then lock it with a padlock. Another more secure option is to drill a neat hole and install a lock inside the box. But the second one is more difficult. The other aspect of securing a storage box is fixing the box itself to the ground so that nobody can lift it off your garden. To do that, you can bolt the entire box down to your patio.