Creating Apps for my sharepoint online team site

Hi,

I have a SharePoint online team site for which I have to create apps.

Now to create app i found that we can create app only for Developer site and then use that app package to app catalog and then insert that app in team site.

Now the problem is to create app on developer site how can i gain access to the list and libraries of team site.

Do i have to create all the list and libraries of team site into developer site and then write code.

I am new to development on online SharePoint.