The Guides tab will appear after the activation of WP Travel Pro where the Tour Guide module is bundled so you have to enable the Tour Guide module by going to Admin Panel > WP Travel > Settings > Modules Settings > Pro Modules
Now, to add the guides to the trip, firstly you have to enable the Guide under the Tabs section of the individual trip.

Then, you can select the guide of your choice

To add the Tour Guide, please refer to the documentation.
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