My generic Chinese tablet has android 5.1 pre installed on it. Here is a link to the ebay page on where I bought it.
How can i install android 6.0 onto it?
i have a same chinese tablet but on my tablet i have android 4.1.1 jellybean. So first you can see how tipe of proccesor you have. Next step is to serch a costum rom for your tablet. (A cyanogenmod is a good choice) But you need to root your tablet (Superuser is a good choice) and you need to install CWM. You can watch on yt step by step. you can watch and you will understand) Thank You.