clarify code command

Author: dmarrazzo

documentation/modules/ROOT/pages/env.adoc

@@ -2,17 +2,17 @@
 
 Environment variables keep your app secure, flexible and organized. Let's take a look at how to pass environment variables to containers. 
 
-== Using an environment variable with your container
+== Changing your application to use an environment variable
 
-Let's edit the Java application you created using Quarkus:
+Edit the _Java Quarkus_ application you created using _Visual Studio Code_ (alternatively you can use your preferred text editor):
 
 [.console-input]
 [source,bash,subs="+macros,+attributes"]
 ----
 code .
 ----
 
-Now edit the `GreetingResource.java` class like this:
+Open the `GreetingResource.java` class and change it like this:
 
 [.console-input]
 [source,java]
@@ -55,6 +55,10 @@ Now, back to terminal, package your project:
 mvn package -DskipTests=true
 ----
 
+== Building the container image
+
+To build an image with an environment variable, you need to add the `ENV` directive to the Containerfile.
+
 Rebuild our image to get the new version of the application:
 
 [.console-input]