where do I place bp-custom.php file?

I have followed the instructions given in this page

https://premium.wpmudev.org/blog/basic-guide-to-creating-a-buddypress-language-file-for-sitewide-label-and-message-editing/

to create the bp-custom.php file

I found the original buddypress.pot file in:

wpcontent/plugins/buddypress

Where do I place the bp-custom.php file?