It's actually 'Account Details > Account Upgrades' but getting there may be a bit sketchy for some because you get there via the 'Avatar' which has no textural aspect displayed and there are possibly those that don't know what an 'Avatar' is once explained.

The original Microsoft interface approach was to have all software functionality via the top menu with nested text so a user can always drill though it. Things have evolved since then though.
It's nice to rid interfaces with text everywhere as in mobile phone interfaces for cleaner uncluttered looking sites. Steve Jobs did wonders there on the iPhone interface and has become the modern approach but it can be abstract at times especially to the uninitiated. A confused user will resort to reading the displayed text in various places and has no idea that standing on one leg while rubbing their belly and patting their head is the correct way to get something to work.

If user donation is better for covering costs for the running of the site (I usually don't click on ads anyway) perhaps a text hyperlink 'Ad Free Upgrade' somewhere up top going straight to 'Account Upgrades' will help those who don't know the site inside and out or perhaps do it via a displayed ad itself for the purpose of a self defeating ad system.

That won't work for someone that has not already subscribed though but if they haven't, an alternative page promoting user subscription and the ad free upgrade option.
Ironically, designing simple things has it's complexities. An 'all roads lead to Rome' solution is bomb proof but only if you're going to Rome. Reading the road signs is also necessary sometimes.