After purchasing the WP Travel Pro from wptravel.io, you will get the license key. You need to add this license key by going to Admin Panel > WP Travel > Settings > License.
Note: In the case of a multisite setup, the single license is valid for all subsites if the license is network activated.
Note: Where can you find the download and license, for this please click here.
For detail assistance regarding how to activate the license key for WP Travel Pro plugin, please click here