OK, So first you must download this http://www.arctablet.com/blog/forum/rk3288-entwicklung-und-customroms-development-and-croms/rk3288-rom-twrpcwm-flash-tool-custom-root-firmware-20150117/

Next, you must have root.  If you don't have root then follow the flashing instructions on the site above.

Now, download something like zarchiver from play store to open the above file.  Open zarchiver from all apps and use it as you would a file manager to navigate to wherever the file above is located (probably /sdcard/download/%file%).  Click the archive which you just downloaded from within zarchiver and select 'extract to ./<archive-name>/'

That will create a sub folder where you are currently working, named after the archive.

Now go in play store and download JRummy Rom Installer.

After it installs, open it.  Be sure to allow root.

Click the three dot menu and select 'Flash Image'.  Make sure that recovery is selected and  then select image to flash.  Here navigate to the folder where you unpacked the archive > inside that folder > rockdev > image > select the screen resolution u want (normally 1920x1280 for R89).

After selecting the IMG you want, read over the flash script, if it looks good press flash, confirm install, and you should be in business!

Cheers!

-SB