To view the global workload of multi-project resources, go to the zone of your choice by clicking on it.
Go to the Gantt tab, then activate the load switch.
The figures that appear represent the remaining capacity in hours for a given day (if your Gantt is set to day mode).
Remaining capacity is calculated as follows :
For a given day : Daily capacity - workload : Remaining capacity
To modify the workload, you can edit from the Gantt the number of hours allocated to resources for their tasks.