help with updates

I'm not sure what to update and where to go to update? My computer is set to
update at a certain time everyday but, I ran a scan from a site and the
results showed I am missing updates? Why don't these updates get installed
with my automatic update? I also don't understand why my automatic update
says I am up to date if these other updates are needed to keep my computer
running and up to date? I appreciate any and all the help anyone may have to
offer.
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MissysaysTHANKS

newcomputeruser