If you wish to develop website with wordpress cms, it’s better to change wordpress logo with your own. There are some method you can do as below:
You can manualy change wordpress logo by replace the original wordpress logo located on http://your-domain/wp-admin/images/wordpress-logo.svg with your own logo.
This is the very easiest method, but wordpress will replace back your logo with wordpress logo when you update / upgrade wordpress.
2. Add some code in function.php
You can modify or add inline css to your header wp-login.php. You can use the login_enqueue_scripts hook to insert CSS into the head of the login page so your logo loads instead. To use the code below, replace the file named site-login-logo.png with the file-name of your logo, and store your logo with your active Theme files in a directory named /images::