How to add language switcher in header to Child themes

I installed WPML.org plugins, want to add language switcher in home page, visible before the user is logged in.

For blogs-mu with BP themes, how I installing to blogs-mu-child?
Where, which line I should to add
<?php do_action('icl_language_selector'); ?>

I tried to add to header.php file,
many time still have error, I don't know how to insert the code at the right place.

Where, which line I should to add

Thanks!