With the MCLeaks Authenticator you can enable support for MCLeaks accounts.
Just download it, start it and click the "MCLeaks" button.
Here you find the steps to install and use the Authenticator:
The MCLeaks-Authenticator is the main software, which is required to use MCLeaks. It modifys your local hosts file settings, as well as your local Java certificate keystore, in order to connect to the MCLeaks-network. A click on the MCLeaks-Button enables MCLeaks-Mode for you anbd a click on the Mojang-Button resets your settings to default. It requires administrator permissions on your machine.