How can I tell which resources have just been added to my library?
If you open your home page any new resources (and/or program updates) will be noted there. They will be at or near the top of the page on the day they were updated.
You can also open your Library (CTRL-L), and sort by "Last Updated." If Last Updated isn't visible you may need to include it in the list of columns visible: right click on the column heads and make sure there is a check-mark next to "Last Updated." NOTE: you may need to scroll the Library browser to the far right to see this column. Then just click on it to sort by date.