Selecting the Sources would be part of the Investigation stage of the Design Cycle. Here we collect information from a range of sources to help us with our goal.
If you were making a children's book to promote writing in young children you might explore some of these areas:
In short, this example shows we can use many different sources, such as interviews with experts (publishers, writers, illustrators, English teachers), book fairs, book shops, videos, websites etc.
You need to record all of your research work in your process journal, showing the information that you have found and how it relates to your project. Look closely at how valuable and reliable that information is and document this also in your process journal.