For each security advisory, affected processors are identified at the Security Center under that specific advisory.
Microcode updates are typically included with operating system (OS) updates from your OS vendor. End users do not have to take any special actions to apply these mitigations other than ensuring that your system OS and drivers are up to date. Contact your OS vendor for information on which OS versions incorporate the latest microcode. Microcode requirements can be found on the Security Center for each specific advisory.
Intel always recommends running the latest microcode for your system by using an updated BIOS or by OS loading of microcode updates if supported by the platform. See the Security Center for each advisory with the latest details on what options are available. This is especially true when mitigating potential side-channel cache exploits.