Creating a workflow to email people with whom I have shared an opportunity

Hi guys
Really simple question, can someone talk me through the steps to create a workflow so that when I share an opportunity with team members they get an email to say this opportunity is available to them

I have figured out the simple mail the record owner etc, but not sure how to mail a 'number' of people when then are added to the team in Dynamics.

I am using CRM 2013 online

Thanks

Kerry