Once logged into Office 365, click the grid of dots in the upper left corner. Then select SharePoint.
Once on the SharePoint Dashboard you will see sites you have followed and recently accessed. Click the site you want to access and you will be able to access the files.
Accessing sites from Outlook
You may need to access SharePoint from Outlook if you cannot see a site you want to access on the SharePoint dashboard.
Click the grid of dots in the upper left corner and select Outlook.
On the left, scroll down to the section labeled Groups.
Select the group you want to access and it will pull up any messages that were sent to the group. Each group should have a welcome email. Select the welcome email and there will be a number of options available to you. Click “Add to the Team Site.”
This will open the associated SharePoint Site.