A powerful plugin that will allow you to add custom code or CSS to your header, footer, sidebar, content or feed.
If your question isn't listed here, please post a comment at the WordPress.org support forum. I monitor the forums on an ongoing basis. If you're looking for more advanced support, please see details here.
Several customization options are available via the Settings page in WordPress Admin. You can access this via Settings » Add to All
If you would like a feature to be added, or if you already have the code for the feature, you can let me know by posting in this forum.