The first step to building apps on JourneyApps is to sign in to OXIDE, the JourneyApps online IDE. Head over to oxide.journeyapps.com and you will be redirected to the JourneyApps Accounts Portal to sign in.
Once you've signed in, you'll arrive on the Admin Portal page, as seen below, and from here you will be able to create new apps or update existing apps from the list (initially this list will be empty - as in the screenshot).
All your apps will be grouped by Organization. By default your account will have two organizations, a "production" organization and a "sandbox" organization. You can switch between Organizations that you have access to using the org dropdown in the top left corner of the screen.