This is a simple tutorial on how to make a manip on Pixlr. (https://pixlr.com/)
It's easy, you'll see.
Open two images on Pixlr. I recommend a tumblr picture, because the quality is better.
You can choose any image you want, I chose these, since my 'couple' will be Tom Hiddleston and Crystal Reed.
Using the Lasso Tool, go around the person that you're going to use. In my case; Crystal Reed.
Copy, close the tab and paste on the other image.
Using the Free Transform, adjust your image so it fits the other.
If you have still some parts off, you can erase it.
It's done! Save your Manip, and, if you want, put some effects on it. I used Picmonkey, but you can feel free to use any other. (http://www.picmonkey.com/)