You can add task bookings in 3 different ways:
1. Click on a ghost booking to convert into a real one.
2. Click on the Add booking button (top left), in-line quick action, or click and drag on the resource schedule the desired booking range.
NOTE: When creating a booking through the Add booking button, you'll be able to add a certain number of hours/day to create an hourly booking.
This will show up under the 1 Day timespan under the View button (top right corner), where hours are displayed horizontally.
NOTE: To change a booking range, hover over an existing booking → pinch the arrows that show up at the start and end of the booking to extend or shorten it.
3. Via the Unscheduled Work tray (at the bottom), that displays all the tasks assigned to a user that are still not scheduled yet (a.k.a. don't have a start and end date).
Open it, then drag and drop the unscheduled tasks on the schedule of a user. Only the user's schedule becomes highlighted to reduce data entry errors.
NOTE: When dropping an unscheduled booking on the timeline, this will default to the remaining hours that are still available for that given day (plus a green checkmark) or alert you that there are no more available hours (via a red cross).