Shifts that are in the Finalise section of the Allocations screen and have a shift status of Member Accepted need to booked with the shift location ( client ).
To book a shift with the client, you need to lock the shift by clicking on the box located between the  symbol and the  symbol
Once you have the shift locked, the blue  then shows as 

To proceed with booking the shift, you need to select Book from the quick action toolbar.

Image Placeholder

When the confirmation screen comes up, type in the Professional's name ( the person you spoke to at the location ) and select Yes to proceed with the booking

Image Placeholder

The shift will then be moved to the Completed section of the Allocations screen and the shift status will now be changed to Shift Booked

Image Placeholder