Hi Helen,

I hope you are well today and thanks for asking!

Which file format image do you have? Rating Manager supports Scalable Vector Graphics (SVG). If your image is JPEG/PNG, then you’ll need to use some converter, for example: http://image.online-convert.com/convert-to-svg or PhotoShop.
When you have the right SVG file, then you need to upload SVG source to Rating Manager > Style > Custom SVG.

See screenshots:
1) https://www.elementous.com/wp-content/uploads/2015/06/rating-manager-style-settings-tab-02.png
2) https://www.elementous.com/wp-content/uploads/2015/06/rating-manager-style-settings-tab-07.png

To change the size of the icon (stars), go to Rating Manager > Style > Icon size.

See screenshot: https://www.elementous.com/wp-content/uploads/2015/06/rating-manager-style-settings-tab-03.png

SVG examples:

Do you have demo setup? If so, then we would be happy to take a closer look.