Checking for patches or updates ESXi 5.1 (free)

Good Morning Support Community,

I'm hoping that you can help me with a question, how can I check that i'm running the most up to date version of ESXi 5.1 on my home server? I tried installing the update manager and it doesn't look like this is an option as a plugin (see image below). what is the best way for checking and installing patches on ESXi (free) version ?

Thanks,

Delmiro