There's no native support for overclocking.
BUT, ASUS pre-built's typically use standard retail motherboards - so you may be able to find a BIOS update that's compatible and will allow it.
Download/run CPU-Z and, under the "mainboard" tab, what is the model number of the board?
https://www.cpuid.com/softwares/cpu-z.html
The Essentio used C2D's at best IIRC, so OCing isn't likely to net you too much headroom at all..... but if you want to explore it, establishing which motherboard is inside would be the place to start.