First of all thank you very much for buying the pro version.
Enabling the setting is quite easy.
For this you simply need to go to Admin Panel > WP Travel > Settings > Addon Setting and enable the addons setting. For the payment go to Admin Panel > WP Travel > Settings > Payment and add the key for your desired payment gateways.
Hope this helps.
If you have any issues further then kindly let us know so that we can help you.