When creating a ticket, use the Assignee dropdown to select the mechanic. As long as they have a Papaya account and have access to the relevant hub, their name will appear in the list, and the ticket will be visible in their account.
If you can't find the mechanic in the list:
Make sure they have been added as a user. See How do I create a new user?
Check that they have access to the hub where the ticket was created by going to Settings > Users > click on the mechanic's name > Hub Access.