Proceed to the "Services" tab on the left nav bar.
Here you will find a service store populated with Services you have the option of adding to your shortcut bar. You are free to add as many Services as you like and any Custom Services you create will appear in this store as well. You will however not be able to see Custom Services created by other Accounts (until approval of Service publication).
To test how a service works, you can add it to your toolbar before pushing live OR use a sample/demo project with Atlas, Telegram, or Signal.
For information about interacting with your shortcut bar on an API level please refer to the Android/iOS implementation documentation.