Your question is a little light on details such as:
1. What HTML are you using to display the images.
2. Do you want to centre the images horizontally, vertically or both.
3. Are the images inter-spaced with text or is the image to appear in the background.
I am going to assume that you want the images centred horizontally, that they are inter-spaced with text, and that you are using HTML similar to the following:
A paragraph of text.
<img src="media/man.png" alt="man" height="160" width="160">
Another paragraph of text.
The following CSS is one way to do the above, it goes in your story's Story Stylesheet area:
Comments
1. What HTML are you using to display the images.
2. Do you want to centre the images horizontally, vertically or both.
3. Are the images inter-spaced with text or is the image to appear in the background.
I am going to assume that you want the images centred horizontally, that they are inter-spaced with text, and that you are using HTML similar to the following: The following CSS is one way to do the above, it goes in your story's Story Stylesheet area: