One of the ways to add resources to your reading lists is to collect them first. To do this you can bookmark resources from the web, by clicking your bookmarking button (see the guide on installing the bookmarking tool). When you click the bookmarking button you can add the resource directly to one of your reading lists or save it to add later on. This is a handy way of collecting resources that you're interested in, before making decisions about where and when you want to include them.
When adding USW Library resources, you can search for, and add them from within the reading list. See the heading Adding resources to your reading list to see how.