Instance* myInstance = /* some instance */; int64_t myValue = 100; // your 64-bit integer value myInstance->SetData64("myKey", myValue);In this example, we first create an instance object and store it in the variable `myInstance`. Then we create a 64-bit integer value (`myValue`), which we will use to set a particular key with the value in the instance. Finally, we call the instance's `SetData64` method to set the value of our 64-bit integer in a key named `"myKey"`. The package library containing the InstanceScript SetData64 function cannot be determined without additional context as it is a specific implementation used in a particular C++ project or application.