Just want index.php, WP site in other directory

Hi – currently my site has an index.html (created in html editor)
The rest of the entire site is done in WP, in a different directory. Want the index.html gone and want a WP index.php. Can I install JUST and index? Obviously don’t want to overwrite current install on rest of site.

Everything is fine with rest of site – links, permalinks all ok. Don’t have to move entire site to root directory – out of the current folder.

Thanks!