Try to extract the zip file of the theme / plugin on your computer, then upload the extracted folder to
yourdomain/htdocs/wp-content/themes if it’s a theme;
yourdomain/htdocs/wp-content/plugins if it’s a plugin, replacing
yourdomain with your domain if you added the subdomain / domain again on your account, with a FTP client. Also, I’ve seen on the file name of the theme you’re trying to install that has
nulled on its name, and I need to warn you that nulled themes / softwares are not allowed on free hosting.