After you download your generated code, get oriented by looking at the Files Overview. You do most of your coding in the XXX_Plugin.php class file.
You may need certain operations to happen during install/uninstall (including making database tables), during activation/deactivation, and during upgrades.
Maybe add short codes
You may need to add some AJAX handlers
Your plugin may need to have options including an options administration page.
You will want to understand how to enforce role security.
You may need to add administration pages.
As a good plugin writer, you will want your plugin to support internationalization.
Once you have your plugin created, you may want to share it. To do this, register your code on WP.org.
You will later want to release and upgrade your plugin.