Upgrade from MacOS 10.12 to 10.13
My iMac is (21.5 inch, Mid 2011) with 2,7 GHz Intel Core i5 an macOS Sierra 10.12.6
I need to upgrade to High Sierra but can't fin a way.
What can I do? Is itt possible, other resources on the net says 10.13 should be possible for 2010 Macs.
iMac