I'm going to guess that you do not have any Cognos experience. Is that a fair statement. What I would suggest is to take our free webinar we offer on Cognos reporting. Do you have our Analyis offering only or do you have our buy-up Intelligence offering? This will determine which class you can sign up for.
Here is the link to our training toolkit to see what classes we are offering: https://www.concurtraining.com/pr/reporting/resources.
But, to put your mind at ease, what you are asking is very easy to do in Cognos. I think you would really benefit from our free webinar. Did I mention the webinar is free?