Update README.md

README.md

@@ -11,6 +11,8 @@ Download the installer here:
 
 <a href="https://github.com/pulibrary/ExcelAlmaLookup/releases/latest/download/CatalogLookupInstaller.exe">CatalogLookupInstaller.exe</a>
 
+(Note: Depending on your computer's security settings, trying to run the installer may pop up a warning that "Windows protected Your PC".  If you receive this warning, you can proceed with the installation by clicking "More info" and then "Run anyway".)
+
 Simply run the installer as the user who will be using the plugin (and be sure to quit Excel before doing so).  After the plugin is installed, a new tab “Library Tools” will appear in the Excel ribbon.  This tab will contain a button labeled “Look Up in Local Catalog”. 
 
 <img src='./img/ribbon.jpg'>