Bookmark as normal. (If we don't have the book in hard copy or the article available in the library, bookmark from Amazon, Google etc.)
If it's a book chapter you want digitised, then you can choose has part from the drop down menu and press Add
Then complete the form by adding fields from the pull down menu.
Choose create & Add to list, choosing which module you want the digitisation available for.
In edit screen, choose request digitisation
Check each screen as you choose next step. Complete as much detail as you can until you can submit request.