You should have a live USB of the distro you want to use and ensure you have backups of all the data you care about. Then the easiest/quickest/least error prone way is to just wipe the whole drive and reinstall the distro from the live USB. They typically have an option to wipe and install things from an empty drive. Then just restore your data from your backups.

You could also, after creating backups, from a live USB environment delete the windows partitions and resize the linux ones - being careful not to delete the EFI partition as that is where the boot loader lives. You can optionally delete the windows boot loader from the EFI partition as well. If done right you should still be able to boot into your linux system afterwards though when missing with partitions like this, especially when you don’t know what you are doing, it can be easy to break the boot systems. These can be fixed from a live environment and there are many guides out there on how to do that.

You can always just reinstall the system again if you mess things up and cannot figure out how to fix them - so always prep for that case by backing up everything you care about first.