how to start over - website

hello,

i'm new, so sorry for the question. i built a site on a given WP theme, and have changed my mind and want to start all over. i've tried to reinstall a new theme, but its funky and i think i'm getting complications because of my previous WP install and various work done on the previous theme. how do i erase all WP-related files and start over? don't need to redo email.

i saw an article once on softaculous and how you can do a WP install with rewrite, but i couldnt get that to work. i was never promoted to rewrite.

thanks!