If you cannot access the main UI, but the system powers up, boot in to recovery.
Try and find out what your recovery keys are (e.g. it's usually vol+, vol- and power on Samsung phones) online or by reading your device's manual, then holding them as your device boots.
Once in recovery, use the volume keys to select an option and power to use that tool, unless your device has a d-pad or older Android style buttons (Menu, Home etcetera).
Also: You can use adb to force the device to reboot to recovery mode if it is enabled, like this, in a terminal or command prompt, with the device connected to a USB port on the computer:
$ path/to/adb reboot recovery on Linux/Mac OS X; and
C:\> path\to\adb.exe reboot recovery on Windows
path\to\adb.exe with the location of adb found in the Android SDK
platform-tools folder (the SDK can be downloaded from http://developer.android.com/sdk/index.html - choose SDK for an existing IDE)