If a worker is already on the TikForce platform (they may be registered with another organization, or even already registered with yours), you should encounter the error message “The email provided is already in use.” when you try to “Add Worker”.
You can use the Search facility (search on email address) to see if the worker is already part of your organization. If found, you can use “Worker/Manage Worker” to view their details, or “Positions/Manage Positions” to “Assign Position” to them.
If the worker is not part of your organization, but already on the TikForce platform, you will need to invite them to your organization.
You do this via “Worker/Manage Invites” to “Invite Worker”. They will need to first accept the invitation, and then you can start to assign positions to them.