Once you've purchased your Guitar Pro 7.5 license key, installation is straightforward:
While Guitar Pro has moved on to version 8, users with a 7.5 key are entitled to free updates to version 7.6. A Cautionary Tale Guitar Pro 7.5 License Key
A single license key typically allows you to install the software on up to 5 computers within the same household. The Update Path: Once you've purchased your Guitar Pro 7