Badly managed permissions can obviously pose a threat to data security, so being able to easily remove sharing links, reset the inheritance of custom permissions that have been inherited from a parent object, and even set permissions for items.

Once you are within the [Explore Sites] menu, click the [Explore] button next to the site which contains your desired items.
Tick the checkboxes of the desired items you wish to manage permissions for. Then click on the [Manage Permissions] button:

Then proceed through the wizard.

If you wish to manage permissions for one single item, you can also click the 3 dots to bring up a context menu: