Clarify dev setup and add `cd` step

developer/setup.md

@@ -9,11 +9,13 @@ Ready to hack on your site? Here's a quick overview.
 
 ## Setting up
 
-Run these commands to get set up.
+After installing Go and Node.js, run the following commands to build, configure, and run the application.
 
 ```bash
 go get -d github.com/writeas/writefreely/cmd/writefreely
 
+cd $GOPATH/src/github.com/writeas/writefreely
+
 # If running Go 1.11+
 export GO111MODULE=on