Apart from single sign-on, its very straight forward.
I guess, when you render a Cognos report you will have report URL right?
use that url in iframe
<iframe src="url" height=500px,width=500px />
But if you don't have single sign-on , you will be asked to login and once you login to Cognos, you should be good to render any report from cognos through browser.
I have integrated OBIEE and BO into our stack so, the need to train normal users is eliminated.