To insert a URL link, click post reply to bring up the text editor. Type whatever text you want, then go back and highlight the selection you would like to make a link. Click the little globe with a paperclip icon above the text edit box. This will bring up a window where you can type your URL. The selected text will then become a click link.
Example: This is a cool place to
learn all about SeaCraft boats.
Hope this helps.