The time clock is only displayed when a statement period has been configured for the user under Base data > Statement, time recording and holiday periods.
Time recording via the time clock can be done via the menu item “Time clock”, in the App, in the Web App or via a central time clock (e.g. on a tablet). Under Base data > Statement, time recording and holiday periods > Time recording you can specify for each employee which time clock they can use to record their time. With the time clock, times for projects, main and subjobs and for the driver’s log can be recorded. The latter is done via the lower dropdown list in the time clock; for the others, select the corresponding one from the upper dropdown list. If certain project types should not be visible in the time clock or only visible for certain user groups, configure this under Administration > Projects > Defaults.
See here how to configure the time clock.