This patch is available only for Windows 10 OS. The patch will install automatically once the PC connects to internet.
There has been multiple reports of some application not being compatible with this latest patch. Certain Antiviruses are causing blue-screen after installing the Meltdown patch.
There has been reports of some SSL VPN applications not connecting to the server after the patch is applied
Antivirus vendors are releasing patch to fix the compatibility issues but it may take a few days for all of them to be available.
I would recommend you to update all the important application installed on the PC before applying this patch to prevent any incompatibility issues.
If you the patch is already installed and there is some critical application causing issues, you can try to uninstall the patch and check if the application works without this patch.