Good question. Our research did not reveal any specific document that provides the order of events for creating a contracts requirement package.  That was expected as this is often scenarion dependent.  We do offer the following suggestion:

Go to the Army Contracting Command webpage. The Procurement Support Division may be able to provide you with something.  I also recommend you go to the RESOURCES tab and open the MAP Application.  When you do this, there is a really cool scenario driven learning tool called Contracting Compass.  The requirements development within Acquisition Strategy will take you to the Requirements Package.

Best of luck.