It's a pain! Repetition is key. Write them all out, draw and colour in diagrams, put up posters all over the house. Maggie Raynor- The Horse Anatomy Workbook is fantastic. I used it as a base for most of my learning.
I'd say it would probably be best to look at simple diagrams of the muscles first and then try and recall which ones you remember by labeling them on an unlabelled diagram. For example, look up the muscles in a horse and view a labeled image. Then cover the labels and try and remember which muscles are which by writing them on an unlabelled diagram before checking. Repeat this and if you're consistent you should remember!