A Job does not have to be worked all at once. Each separate scheduled date and time is called a Visit. Visits can be unassigned (no employee) or scheduled (an employee is assigned for the date and time.)
To assign two employees to a Job at the same time, create two separate visits on the same date and time and assign each to a different employee. To make this easier, you can make one visit and assign it to the first employee, then click on the visit and choose Add Visit. This will allow you to pick the same time on the dashboard for another employee and create that Visit.