First at all backup all you important files to a EXTERNAL SD-Card.

Prepare Computer
Download the firmware that you want to install. It should be a .img file (after unzip)
http://uploading.com/files/get/c7d9469b/n101%25E7%2599%25BD%25E7%2589%258C.rar
Sometimes there will be extra files included that require. (you can use them or just follow this guide)
Reason why not use the extra files? Because there is a chance that the program set on Chinese language.

Then you need the Rockchip tool to flash your device. This can be download on the link below:
https://www.dropbox.com/s/eyy3gpaas8fejz6/Rockchip_flash_tool.rar

Unzip them and you will found an RKBatchTool.

Prepare Tab
Go to your device and shutdown them.
Connect the USB cable with your device.
Hold the “power” + “Volume -” button for about 3 seconds.
Release both of them
You will see a black screen, it won’t appear anything on the screen.

Connection with Computer
Connect the USB cable to your PC
If you connect them for the first time in recovery mode it will ask you to install the driver
The required driver can be found on the following link:
https://www.dropbox.com/s/2eqo5dcsu5bbhki/RockusbDriver.rar

Flashing the Tab
If everything correct done you can start the RKBatchTool
On the top of the program you can click on the “…” (browser button) and select the IMG file that you want to update.

Then look below on the connected Devices NO1 is green or not.
If the color is pink, click SWITCH to change it to green.
Select then on the UPGRADE button (NOT RESTORE!!!)

And just wait until it ready. Do not interrupt the device while it is flashing.. Otherwise it can brick your device.