Update README.md

Author: timhall

README.md

@@ -7,7 +7,7 @@ Getting started
 ---------------
 
 1. Download the [latest release (v3.0.7)](https://github.com/timhall/Excel-REST/releases)
-2. `Excel-REST - Blank.xlsm` has everything setup and ready to go.
+2. To install in an existing file, run `install.bat` to walk through installation. To start from scratch, `Excel-REST - Blank.xlsm` has everything setup and ready to go.
 
 For more details see the [Wiki](https://github.com/timhall/Excel-REST/wiki)