As it seems a little bit confused on how you can manage your SharePoint on Office 365, here is an how to

First, connect to the Office 365 portal and click on the Admin link shown at the top

from https://portal.microsoftonline.com/

From this page, you have some links to manage Exchange, SharePoint or Lync (as well some of your Office 365 tenant settings [internet domains, user…])

Below, Office 365 you have a Manage link for SharePoint

This link will redirect you to the SharePoint tenant administration page (the URL is like -admin.sharepoint.com">https://<youdomain>-admin.sharepoint.com where <yourdomain> is the one you associated when you have created your Office 365 tenant (youdomain.onmicrosoft.com)

From this page, you can manage SharePoint site collections, InfoPath services, User Profiles and Term Store

To manage your SharePoint Site Collections (settings, creation, deletion…) click on Manage Site Collections