If work effort is required that cannot be satisfied by current team member availability, you can modify availability to meet the work required.
Click the Convert ETC to forecast toolbar button.
Availability is changed to exactly match work effort as defined on the Work sheet. Where there was availability and no work is defined, availability is set to zero (0). By definition, all cells that have work also have availability, so the cells have clear background.
Note: A clear cell on the Work sheet means there is availability for that resource ON THE TEAM SHEET. There may be no work required from that resource on that task in that time period, so the cell will be empty and clear.
Task assignment highlighting after Convert ETC
Availability after conversion