According to the setting which your chief chose, you might need to accept or deny working hours.
Accepting or denying working hours goes as follows:
Choose in the menu for My schedule - My working hours.
Now you'll end up in one of the different screens:
Click on the day which you'd like to accept an click on the green
check mark to accept or the red cross to deny.
On desktop/tablet, calender view:
Brose through the weeks and click on a working time on the right (on a tablet you need to hold it for a while). Then click on 'Accept' or 'Deny'.
On desktop/tablet, classic view:
Choose the working time which you'd like to accept or deny and click in the row on the checkmark or the cross.
Hint: you can switch between the classic and calender view by clicking on the link at the top of the page.