how to reinstall windows 10 using bootcamp

Hi everyone

I have been looking to reinstall windows on bootcamp as running slow.

I tried bootcamp assist

It managed to put windows onto a usb drive, but then it stop at window helper telling me to install those when installing windows?

From what I remember when i first installed it, bootcamp did it all for you?

Or do I just reinstall from windows directly now that there is an old copy of windows already? and how would i do that? can it be done with the usb made by bootcamp?

Cheers everyone