htacces file problem, please help

hello, (i have two domains and one hosting) in one domain i have the wordpress installed when i access the second domain it loads the first domain with the wordpress website

how can i modify the htacces file so when the second domain is accessed to not load the word press website from the first domain? ( to give error or something that website doesn’t exist )

The wordpress is installed in a subfolder /blog
Below is my htacess file how i need to modify it?

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteBase /blog/
</IfModule>
# END WordPress
rewriterule ^index\.php$ – [L]
rewritecond %{REQUEST_FILENAME} !-f
rewritecond %{REQUEST_FILENAME} !-d
rewriterule . /blog/index.php [L]