map subdomain to subdirectory install

Greetings 🙂

first of all i have 2 seperate WP installs
– one in the htdocs root “www.example.com”
– and one in a subdirectory “www.example.com/subdir”

The Hosting provider has no cPanel but stated the subdomain “subd.example.com” is ready to be redirected through and index.php or someting… dunno i`m not used to that since i usually saet them in a cPanel myself.

anyway
now i`d need to know how to setup the redirector so that it points the sobdomain to just the subdirectory install in a save way

my attempts failed since i only get to the htdoc root install but not the subdir

Thanks a lot in advance 🙂

Cheers!