Default setting for user team when creating new opportunities

Sage CRM 7.2h

How do I get my fields for "Assigned To" and "Team" to automatically populate with the User's name and team? When filling out the New opportunity page, we would like to be able to have these fields auto populate so that they don't have to manually do this. I am a newbie to this and not comfortable putting in code so please explain in detail what to do so I can copy exactly your instructions.