As Muzza said, yep, you make your network diagram right in Project. Once you have resources assigned to each work package and a network diagram made, then project will automagically create the schedule and Gantt chart for you. It will also identify the critical path(s).

If you have tasks that are not dependent on other tasks, then just put them as parallel paths in the network diagram. A project with no interdependencies would look like a bunch of resistors in parallel (one task per segment). If you have a complete and thorough WBS, then take the time to diagram out every single work package in a network diagram. Then, after you put resources and estimates on each work package, Project will make the schedule for you (which you may need to edit).

Jim