Things you need to make it work:-1. Have two drag and drop fields in component dialog- yes you can have it2. Component - HTML + CSS which takes these images as input.3. Make sure CSS displays image based on viewport4. Go to Desktop view you should see desktop image5. Go to Mobile view you should se...
You can use the template editor to create your own template for XF.It allows you to define clientlibs for template without writing any code.https://helpx.adobe.com/experience-manager/6-4/sites/authoring/using/templates.html
Technically CF is also of type asset.Main idea is to create content which can be reused and independent of design.Since you already have an image in DAM, putting it inside CF and then using it- I don't see how it helps.
There is no official documentation or steps released to do this.But you can try to look at OOTB one and do it. I don't think it will be straight forward.