The first step is to define exactly the problem, is not the same as a tablet that does not turn a tablet getting stuck in the Android logo or brand stays are different situations.
A second step is to try to charge the battery as it may be that the tablet is completely discharged and that is the reason why not turn.
The third logical step is to try to do a factory reset which is achieved in two ways:
a) By a reset or reset which usually include some tablets
b) By entering the recovery mode (hard reset)
Unfortunately not all tablets have reset button or recovery mode, in any case, it is not always easy to find and reset the tablet, which is why we recommend searching the manual from the manufacturer's website.