How to Upgrade an OS X El Captain 10.11.6?

[tsuche]

Hi
I am new to upgrading!! I was given an OS X E1 Captain 10.11.6 and need to upgrade it to download Internet Security. I tried to use what was suggested and a message "This version of macOS 10.13.6 cannot be installed on this computer." Will this computer upgrade?
I have never done anything in upgrading.
Thank you so much.
tsuche

 

[CooperBox]

You ask, "Will this computer upgrade?"
Which computer are you talking about? Depending on the model it may not support OS Sierra or later OS's.

 

[tsuche]

You ask, "Will this computer upgrade?"
Which computer are you talking about? Depending on the model it may not support OS Sierra or later OS's.

OS X El Captain 10.11.6 I have never owned a Mac so I don't know much about them.

 

[CooperBox]

OS X El Captain 10.11.6 is the Apple Operating system. What Mac do you have? iMac, MacBook, MacBook Air, MacBook Pro, etc? And what exactly is the year and model reference number? Some but not all of these can be upgraded from El Capitan.

 

[KeesMacPro]

If you go to : About this Mac > System Info , you'll see what model you have.
A screenshot would be very helpful.