Use the WBS and manpower availability to build a project model
Steps to take
Now match people to jobs. Wherever possible try to ensure that there is only one resource per task. Ensure that, as far as possible, every job has a human being's name as opposed to an organization or a "TBD" or "ANO" against it.
Ensure that, as far as is possible, you have used each person's time available to the project exactly no more, no less.
If you are using a PC-based tool, use it to assign people to jobs. The tool will now draw a Gantt chart of your project for you. Among dozens, if not hundreds of useful things, the tool will show you your project's critical path .
Failing this you will have to draw the Gantt chart yourself manually. If you are doing this, be warned that the manual approach will almost certainly introduce errors. The Gantt chart is a model of how your project may unfold over time.