Hi, I'm farely new to omeka. I'm working to create a library with accessabel content for people with disabilities. There's a list of fields for collections and items in the collections. I was wondering if there is a way to add my own field to replace the ones that is there and how can I go about doing it. also the next thing I want to do is have an option to upload the digital content where it can have a link to the item for download.