Since the LootLocker SDK was installed either through the Unreal Marketplace or the GitHub repository, updating it means getting the latest version through that same method.
Update through Unreal Marketplace
Open the Epic Games Launcher, go to your Library, and check the Vault section for available updates to the LootLocker SDK plugin. If an update is available, click Update to install the latest version, then follow the same installation steps to make sure the plugin is enabled in your project.
Update through GitHub
Download or pull the latest release from the LootLocker Unreal SDK GitHub repository and replace the existing LootLockerSDK folder in your project's Plugins directory with the new files, following the same installation steps you used originally.