If a worker ever contacts you and tells you that they had never received the invitation you had sent them - do not be alarmed. Some cellphone service providers block business text messages.
The text message invitation is a formality and it includes a link to the appstore to download the Workyard application.
After you have added them to Workyard they can go to the Appstore on their phones and download the Workyard app and login.
If you would like to send them the link via email here are the links: