There are several ways to link presentations from one to another. The downside of linking however, is the fear of link breaking when moving the files from one location to another. A solution to resolve this is to make use of embedding.
To embed a PowerPoint in a PowerPoint, click Insert > Object. Select Create from file, then click on Browse. Look for the ppt file you want to embed. Then click Ok twice. The file will then be embedded with the first slide shown as a thumbnail. There are two ways to open the embedded presentation during slide show view. The first one is to click on the thumbnail, which will open up the embedded presentation.
If you prefer to have it open automatically, click Slide Show > Custom Animation. Select the thumbnail, click Add Effect > Object Actions > Show. Lastly, set the Start from “On Click” to “After Previous”.