EndNote uses four methods to lookup full-text documents for the citations in your library; three of these are automatic, but you'll need to configure the fourth.
In EndNote, open the EndNote preferences and switch to the Find Full Text sections. Enter
http://su8bj7jh4j.search.serialssolutions.com/ for the OpenURL Path.
https://login.ezproxy.lib.vt.edu/login for the Authentication URL (this make use of the Off Campus Sign In service).
Now EndNote will make use of all standard methods for connecting to full-text documents available from the Virginia Tech Libraries.