URL ShortCodes plugin adds support for a basic short codes to use in your post/page editor that produce correct absolute URLs.
There are 2 ways of installation. If your setup supports it, you can search for the plugin, by name, within your WordPress control panel and install it from there.
Alternatively, you download the .zip file, unzip it, and copy the resultant
url_short_codes folder to the
wp-content/plugins/ folder of your WordPress instaltion folder.