My iPhone wont turn on how do i fix this

You probably fix it by taking the phone to the Apple Store or an authorized Apple Service shop.

But as a last resort before you head to the shop, try a Forced Restart.

Force restart iPhone - Apple Support, which is also known as If your iPhone won't turn on or is frozen - Apple Support

There are only 2 possible results:

1) The phone returns to normal operation

or....

2) There is a hardware problem with the phone that will need attention at the Apple Store (make an appointment) or at an authorized Apple Service shop

Find Locations

See this article.

If your iPhone won't turn on or is frozen - Apple Support