Let’s assume the following: you’ve got a great PowerPoint presentation that you want to include within your Office 365 Team Site (or basically, anywhere else in a Office 365 SharePoint site) as a slide show. So instead of people downloading the file you want to show the presentation’s contents in the browser. In this article, we will go through the necessary steps to do so.
Please note that this only works for the P1, E2, E3, and E4 plans, but not the E1 plan, as Office Web Apps is required.
What you need are two things: a PowerPoint presentation stored somewhere in your Office 365 site as well as a page on which you want to show this presentation.
First, we need to get a link that will show the PowerPoint presentation as a slide show. Navigate to your presentation, and click on it, which should open it in the browser in Office Web Apps in most cases. If it doesn’t, you can alternatively open the presentation’s item menu and select View in Browser: 
Once the presentation is shown in the browser, click on Start Slide Show: 
A new window opens up and shows the slide show of your presentation, exactly what we want to include in a page! Copy the full URL from the top of your browser bar: 
The URL looks something like this: https://yourprefix.sharepoint.com/_layouts/PowerPointFrame.aspx?PowerPointView=SlideShowView&d=F5f4d162c52074cbbb155aac5fd9a0757made
9147475d24ed684e8675780ee05e4mee276220818a4b288f1e63652eab84dcm (or starting with https://www.yourdomain.com/teamsite/., depending on if you set up your domain)
The second step now is to include this slide show in your page. SharePoint provides us with a so-called Page Viewer Web Part that simply displays the contents of a specified URL within your page.
Open the page on which you want to display the slide show and edit it :
Click where you want to add the web part on your page, and from the Ribbon select Insert and More Web Parts: 
Filter by Media and Content, select Page Viewer, and click Add: 
The Page Viewer Web Part is added to your page. Click on open the tool pane 
The tool pane opens to the right. Paste the URL that you copied before into the Link field. 
Expand Appearance, and enter a desired height and/or width (you should preferably enter a height as to display your slide show in a specific size). Please note that you can also change that title under Title, which is set to Page Viewer by default 
Once you click Ok, you can see the final result in your browser: 
Click Save & Close to save your changes. That’s it!