Hello kristincammeyer,
For Office 365 users, we can use Microsoft Office Web Apps in SharePoint by storing documents in the SharePoint library. Then, open documents in the web browser to view and edit them.
We can create a PowerPoint library in SharePoint Online, here are the steps:
1.For Office 365 for Enterprises plan, make sure you have assigned Office Web Apps license to your user.
•Log into Office 365 Portal, click Users in the left pane of Admin page.
•Click your user, and in the Assign Licenses page, make sure Office Web Apps is checked.
2.Go to your Team Site, click Site Actions->New Document Library.
3.Type a name, select a Microsoft PowerPoint document template, and click Create.
4.Click New Document under Documents tab to create a new PowerPoint document.
Besides, for Office 365 for Professionals and Small Businesses, we can easily find the PowerPoint Web App by clicking Documents in the Team Site.
For your reference:
Introduction to Office Web Apps
Start using Office Web Apps in SharePoint 2010
Regards,
Cherry Wang