How do you run development signed with an embedded app?

In Apple's In-App Purchase Programming Guide, I read the following tip when it comes to testing in-app purchases with a Sandbox test.

Create a test user account in iTunes Connect.

On an iOS device for development, sign out of the App Store in Settings.

Then build and run the app from Xcode.

Use your app to make an in-app purchase. When prompted to sign in to the App Store, use your test account.

Note that the text "[Environment: Sandbox]" appears as a part that indicates that you are connected to a test environment. If the text "[Environment: Sandbox]" is not displayed, you are using a production environment. Make sure you use signed development to build your application. Manufacturing signatures use a manufacturing environment.

My question is, how do I make sure I run my development signed program? Where exactly is this done and what steps should I follow?