You can send a link to the workrest app directly from your device.
To do so, when you're next logged into the workrest app:
Click Menu, bottom right of your screen
Tap on the "Invite Others" button
Select the contacts you want to invite
You can also send the invite to a group chat
The contacts you invite will receive a link connecting them to their applicable app store (IOS / Android - this is set based on the recipient's device).