1.Login to your dashboard--> layout- ->Page Elements
2.Click on 'Add a Gadget' on the sidebar.
3.Select 'HTML/Javascript' and add the code given below and click save.
<iframe height="400" width="90%" frameBorder="0" src="URL OF WEB PAGE">your browser does not support IFRAMEs</iframe>


Note :
 Remember to replace URL OF WEB PAGE,with the url you want to embed into your site.You can change height,width.

Look at the example below.
<iframe height="400" width="90%" frameBorder="0" src="http://google.com">your browser does not support IFRAMEs</iframe>
Now you are done.