There are differences between how to access the full retail version of FM from the Early Access Beta version, and it largely depends on which platform that you are playing Football Manager on.
For all platforms, you can continue playing the save game from the Early Access Beta version.
If you are playing Football Manager Early Access Beta on Microsoft Store, you will need to download and install the full retail version separately when it is fully released.
Once you have installed the full retail version and checked you can access your save file, you are free to uninstall the Early Access Beta version.
Rest assured that your save games won’t be deleted when you uninstall the Early Access Beta version.
If nothing above works, please submit a support request stating exactly what you've tried so far, and a member of our team will try to help.