I only know how to do it in Photoshop, and there is no "stitching" feature in photoshop. Hopefully though, the following will clue you in if you want to do it in PSE.

Create a new image. Make it's canvas big enought to hold all five images of the puppy (it can be bigger than that and you can crop it later).

Open the puppy image. Select|All, Edit|Copy. Go to the New Image and Edit|Paste. Then Edit|Paste again.

Now look at the layers pallet - you have two layers of the puppy. You can use the move tool to move them around, use shortcuts to make sure they snap to each other, etc. but the point is this:

You simply copy/paste then use the move tool to align them.

I assume you can do something similar in PSE. If not and you need to make the images seamless in PS, you can always come back and ask.