Question: I dragged an image(tried both jpg and tiff) to a GIF file and Preview just opens up two documents in one window, instead of adding the image to the first document (GIF). I have Preview 10.0.

[![Picture of what Preview looks like when I try to add 'computer screen' to the file 'happy girl on desk'.](https://i.stack.imgur.com/x56WT.png)](https://i.stack.imgur.com/x56WT.png)

Answer: 
Preview is **not** an image editor. It's a *viewer*.

To create images, you need something that allows you to do this. You can get paid applications to do this and there are FOSS (Free Open Source) tools available. Some of the more popular ones are:

* [Adobe Illustrator](https://www.adobe.com/products/illustrator.html) (Commercial illustration software)
* [Adobe Photoshop](https://www.adobe.com/products/photoshop.html) (Commerical photo editing software)
* [GIMP](https://www.gimp.org/) (Open Source Alternative to Photoshop)
* [Pinta](https://pinta-project.com/pintaproject/pinta/) (Like the award winning Paint.NET for Windows)
* [Tux Paint](http://tuxpaint.org/) (Award winning paint program for kids)

There are many, many more available on the App store and online. 

And if actual photo editing software isn't your cup of tea, Word Processing programs like Microsoft Word has rudimentary image editing built in.
Preview is simple but powerful, and you can add images, remove parts of images, and if you need to edit slides in animated gifs you can. 

Click on view and show markup tool bar for the tools to appear. 

You can do a lot more editing in Preview than you can do in word.

Even Apple says ya can.

<https://support.apple.com/en-us/HT201740>

A little more in depth here.

<http://teach.southwales.ac.uk/media/images-edit-mac/>