Redirect/ htaccess

How can I redirect the domain.XX to domain.xx/subdir?

I cannot change the domain path but, maybe using an htaccess, make a temp redirect.

I cannot create or upload a .htaccess file by ftp… why?

Somebody else is trying the same here:

As for not making a .htaccess, which FTP client are you using? You need to set it to show hidden/invisible files. Files that start with a dot won’t typically show up in FTP programs. Can you create some other file in the same place?