I have also just purchased the Acer home server that came with a trial version of McAfee Total Protection Service. Note that this is a "home server" product running Windows Home Server and is not an enterprise or business product.
I have carefully followed any instructions or links trying to find a way to activate, or even buy, this product but there does not seem to be a way to do it. There is supposed to be an "activation" link in the common tasks of the McAfee tab on the WHS console.
It is not there. Nor is there any way to buy the product.
The software came pre-installed as an "add-in" in WHS on this Acer unit. If you go to the add-ins portion of the setup page the McAfee product is not listed as either an installed add-in, or one available to be installed.
Despite this I get frequent warnings that my home server is not protected and the McAfee product needs to be activated.
I am not a stranger to computers. I work in IT with 25+ years of experience, but this product seems determined to make it frustrating to impossible to activate and use.