You need to state at least two things when asking a question:
1. Which version of the Twine application you are using, because they have different features.
2. Which Story Format you are using, because answers can be different for each one.
A method that works in all of the above is to use a HTMLimg element. The following would be placed within a passage and you would change the "name-of-image-file" part of the code with the actual name (URL) of your image file.
<img src="name-of-image-file">
note: The image file would need to be stored in a location accessible to the Story HTML file you create via either the Build menu item or the Publish to File option depending on the version of Twine you are using.
Comments
1. Which version of the Twine application you are using, because they have different features.
2. Which Story Format you are using, because answers can be different for each one.
A method that works in all of the above is to use a HTMLimg element. The following would be placed within a passage and you would change the "name-of-image-file" part of the code with the actual name (URL) of your image file. note: The image file would need to be stored in a location accessible to the Story HTML file you create via either the Build menu item or the Publish to File option depending on the version of Twine you are using.