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Generally, you put the .htaccess file in your website's main directory. 
However, the location ultimately depends on what you're attempting to do with the .htaccess file

Your .htaccess file (and any changes that you make to it) should be reflected on the live site immediately. 
You do not need to reload your site's Apache service, although external caching services such as Cloudflare might need their caches flushed.