Using new I-Agree (BETA Release) WordPress plugin you can add custom text, links etc like terms and conditions which needs to be ticked before to make login from WordPress login screen. The plugin text is customizable, you can add all text there on login box or create a new Terms & Conditions page, copy its link and add there as shown in the following screenshot.
Simply install and activate I-Agree plugin, after activation visit your admin area Dashboard -> Settings -> I-Agreen (Options) page and add ‘Failed to agree error message’ and ‘Text that goes right after the checkbox’ (you can use HTML), now update the options.