In order to install more apps, you need to root your device and link the appps to external SD.
- Get root master here
http://www.androidfreeware.net/get-root-master.html
- Perform root
- Install Link2SD from PlayStore
- Format SD-card with a LINUX-PC (or boot from Linux Mint Live CD and run gparted): 1st partition (SD-size minus 1GB or 512MB) FAT32 (primary), 2nd partition (1GB or 512MB) ext2 (primary). Be sure to format SD-card and not your hard disk!
- Insert SD, start device and run Link2SD, select "mount at startup" and reboot.
- Use Link2SD to link files to ext2-partition. You can set Link2SD to automatic link mode.
Hint: If you want a native Android UI, install Apex launcher from PlayStore and Chrome-theme in black and white. You can switch back to Arta's UI any time in Apex settings.
Unfortunately Arta only offers a stripped down version of recovery mode, so no nandroid backup can be made. Before tinkering with your device I recommend downloading the appropriate update.zip file for your device here
https://onyx-boox.com/support/firmware-android/ and put it on your SD-card first. In case you have messed up, start device with home-button pressed to start recovery which offers the option to install update.zip from external SD-card. Do a factory reset before installation.