The OS installation depends entirely on how much flexibility the tablet possesses. It can be done, as usual, using the Recovery menu or a third-party tool. While the first method works 100 %, the second one is, on the opposite side, 100 % unsafe because it might damage your device. SO I advise to follow the first path. Turn off the tablet, then press Volume Up + Power until the Android logo shows up. Select Wipe Data/Factory Reset using volume buttons and confirm the operation with Power. Reboot the tablet and the OS should be re-installed.