Well, if you’ve already read this https://codex.buddypress.org/how-to-guides/modifying-the-buddypress-admin-bar/ and maybe this https://buddypress.org/forums/topic.php?id=2283, and do not understand, unless you are prepared to further your understanding of PHP and WordPress’ API, you need to find a developer to write the code for you.
Here’s a little something to try.
Create a “bp-custom.php” file in your /wp-content/plugins/ directory.
Put in the following code:
echo '<li class="no-arrow"><a href=""YOUR LINK"><img src="YOUR BUTTON" alt="" /></a></li>';
add_action('bp_adminbar_menus', 'my_new_buddybar_button', 101);
Untested, but should work…
Change “101” to where your button should be.
eg. “1” would move it to the beginning (right after the BP logo)
to be fair to the OP, i think the buddypress admin bar documentation is quite difficult to follow. i imagine that it would be even more difficult for anyone whose first language is not english.
(for example: “To change a function that is triggered by an action you have to unhook the current function that responds to the action and supply your own function that replaces the core function and then replace the add_action() call with one that responds to the same hook as the original function.”…)