You can find step-by-step guidance on the MXQ Project YouTube Channel
The best high-quality download is the STOCK MXQ_PRO_805_11_Lollipop_20161221.img – it is the last official build before manufacturers abandoned the S805.
This guide provides a professional walkthrough on sourcing, identifying, and flashing high-quality MXQ Amlogic S805 Android 5.1.1 Lollipop firmware.
: Standard software for flashing .img files via a PC and USB-to-USB cable.
Have a unique board revision not covered here? Visit the FreakTab forums or comment below (with your photo) for personalized help.
Sites like China Gadgets Reviews and AndroidFileHost host various firmware versions for the Amlogic S805