You bought a CD, madness.

MacOS Sierra 10.12.1 dmg for mac free. download full version. MacOS Sierra 10.12.1(16B25) offline installer complete setup for mac OS direct link. Whether you want to upgrade your MacOS Sierra 10.12.5 to the latest version or you want to clean install of MacOS Sierra 10.12.6 on your Mac system, you need to download MacOS Sierra dmg file. When you download MacOS Sierra 10.12.6 stand-alone installer, you can perform the installation on your system. Apple recommends the Mac users to update the MacOS systems to the latest MacOS Sierra 10.12.6.

If you want to upgrade your Mac from Yosemite to another newer OS you have three alternatives..

El Capitan, Sierra and High Sierra are all available for download and are free.

It sounds like you have been trying to install updates to El Capitan downloaded from the Apple Support Downloads pages. If so you need to have already installed El Capitan, that is why you are getting the message about 10.11.

for example if you downloaded the 10.11.6 Combo update this will update any previous version of El Capitan from 10.11.0 to 10.11.5 to the last version 10.11.6. Please remember full versions of OS's are only available via the Mac App Store.

Depending on the age of your Mac you may not be able to upgrade to Sierra or High Sierra, if so you should be able to upgrade to El Capitan.

Have a look at the links below to determine what OS you would like to download. Bear in mind though that if your Mac qualifies for High Sierra then you will be denied the download of El Capitan.

Mac Os X 10.13 Download

The versions that will be downloaded in each case will be the latest versions of each OS, so for El Capitan it will be 10.11.6, Sierra will be 10.12.6 and High Sierra will be 10.13.3.

Apple Os 10.12 Download

If you tried Erics link to El Capitan and you couldn't download it, then the App Store is recognising that you Mac qualifies for High Sierra, so you can upgrade to that or if you want you could also upgrade to Sierra from the link above.