How to translate images
Try to avoid having text on images. If there are images that contain text, you will need to go through the potentially difficult and time-consuming process of editing every image just to translate a few words. Remember that the translated image should not have any words in the original language.
If you must put text on images, use image-editing software that is accessible to others who might need to work on the file after you. Make sure that source files are stored in a way that is transparent for others.
If you have an image with text on it and you have no access to the source file, you can edit it in PowerPoint. Just use transparent or coloured text boxes. It may not look pretty, but at least it will be translated.
For more complex edits, ask someone that has access to Adobe Photoshop to edit and prepare the file for you.