I need to have two different email accounts running concurrently but can't find anything in the help articles

Dear community, I'm planning to change my email provider and during the transition period I need to have the old and new accounts running concurrently. The help article states: ".....you can create additional profiles, each with their own set of account configurations, messages, etc. (Note, '''''each profile can access multiple email accounts'''''''.) . but I can't see how this would work. If anyone can explain in simple terms how to achieve this, or point me to the relevant information I should be most grateful.