Note that Planyard is not built originally for time-tracking your team. However, there are workarounds.
Time-tracking employees without giving full project access
What probably makes the most sense, is creating a new category under "Subcontractors". Call it "Employees", for example.
The next step is to create a subcontract with your employees for the relevant line-items in the budget. As you're dealing with time, the unit for the line-items should be set to "hour".
The employees can then submit hours worked the same way subcontractors would - through progress reporting against the contract (also called valuations, claims and pay applications - depending on the country).
The employee will only see their contract-associated line-items in the progress reporting view and they can also suggest extra works (also called change orders and variations). They will also have to selected the period worked and can add comments.
The actual time-tracking can be done with external tools (such as Toggl).
Time-tracking employees with full project access
Another way is giving employees access to the full project and letting them enter the hours worked on directly into the budget.