Is ubuntu supports on Lenovo g5070 and how to install...
Yes, I quickly googled the specs of it and it's much more than enough to install ubuntu. And it seems, it comes with preinstalled dos. If yours have it too, then you can either install ubuntu along with it or you can remove the dos os giving everything to ubuntu.
In either case, you would require a live cd of ubuntu. What you need to do is first download the version of ubuntu you want to install ( I would recommend 14.04 ) and get a usb drive (2 gb would be fine). Use start up disk creater ( if you have access to linux based os on some other computer) or universal usb installer (in case of windows) to make installation disk of ubuntu.
Boot from the usb and simply follow the instructions. This link might be useful.