WP Travel is a bundle of all the addons available. If you purchase the pro plugin you will get all the addon within that plugin. You do not need to separately add any other plugins.
After downloading the pro plugin from your ThemePalace account upload the pro plugin and activate. After that go to Admin Panel > WP Travel > Settings > Addon Setting and enable whichever functionality you would like to use.
For any confusion further, please refer to the plugin official documentation below: