Enter your Search in VIRGO, then click to "See all results" at the top of the results. Use the orange icon in the upper right to get the RSS URL to add to Feedly. Works with both book and article searches. Note that the article search is only for articles that UVa provides ONLINE access to.
Conduct your search, then click on "Create Alert" next to the search bar. Grab the URL next to the orange RSS icon, and enter it into your Feedly account.