How to insert source code in the post

NO easy way. BUT plugin’s help you out.

We installed this plugin, it works great:

Crayon Syntax Highlighter
http://wordpress.org/plugins/crayon-syntax-highlighter/

After installing and activating this plugin, you will see a new button CRAYON in Editor, click it to enter your source code, then click ADD, then you got this:

<div id="TopFlashID">
<center>
<embed src="http://billiga-resor.info/images/falsh001.swf" width="100%" height="120"></embed>
</center>
</div>