This is an excellent website to learn about x-ray interpretation. The website is free to access and has different modules that can be worked through. There is the option to purchase assessment modules with attached CPD accreditation.
I highly recommend you work through the MSK / Trauma tutorials as these will be really useful for your time in the ED.
This image shows the Ottawa Ankle Rule that is useful for the assessment of ankle injuries. If you click the picture you will be taken to a short You Tube video demonstrating the assessment of an ankle using these principles.