MagentoFrameworkComponentComponentRegistrar::register(
            MagentoFrameworkComponentComponentRegistrar::MODULE,
            'Vendor_ModuleName',
            __DIR__
        );

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
        <module name="Vendor_ModuleName" setup_version="1.0.0" />
    </config>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="ThirdPartyVendorThirdpartyModuleBlockFile.php" type="VendorModuleNameBlockFile.php"/>
</config>

namespace VendorModuleBlock;
use ThirdPartyVendorThirdpartyModuleBlockFile as ThirdPartyFile;

class File extends ThirdPartyFile
{
...........
...........
}

bin/magento setup:di:compile
 bin/magento c:f