If you are installing Windows 10 from bootable installation media (a USB drive or a DVD) it doesn't matter how messed up your computer is. Your hard drive could be completely unbootable - even blank. It doesn't matter, because you're not booting from the hard drive - you're booting from the USB flash drive or DVD.
The installation media will set itself up in your computer's RAM and install Windows to the hard drive, in effect over-writing everything currently on the hard drive. There's nothing difficult about this, and I'm not saying that to be facetious.
What's not clear from your original question is whether you purchased a bootable Windows 10 installation USB drive or DVD. If you did, then the only 'trick' is to figure out how to make your computer boot from the installation media and not from the hard drive.
That's an easy question for your computer manufacturer's technical support, if it isn't in the computer's owners manual. Or tell us what make and model of computer you have and someone will look it up for you. Typically you need to press a specific F key while the computer is booting, but there are other ways to accomplish the same thing.
If you didn't purchase bootable installation media, you'll have to create it on your own. Not to worry, we can help you with that. It just requires a few more technical procedures. Nothing you can't handle.