* The things what you need: 3G broadband USB modem stick like Huawei GSM/UMTS Stick and O2 Germany or ZTE 3565-z UMTS Stick, an OTG cable that you could buy from Amazon.
* You have to root your tablet first, and download and insatll PPP Widget by Josua Dietze from Google Play store. This usb_modeswitch tool enables fully Internet access over almost any USB device.
* Connect the 3G dongle with OTG cable and the tablet. Open the PPP Widget, tap configure button and type your user name and password. Once you've done, tap Connect button.