As you will have gathered there are different ways of entering and viewing data within project professional. Here are some of the ways to view critical tasks on your project; 
Detail Gantt View Gantt Chart Formatting Wizard Built-in filter for Critical Tasks Built-in Group for Critical Tasks
But first let’s recap on the definition of critical task/Path. This is best understood as “the series of tasks that must be completed on schedule for a project to finish on schedule. Each task on the critical path is a critical task”. If one task on the critical path moves, the end date of the project will move as well.
As you update your project by modifying tasks, be aware of the critical tasks and that changes to them will affect your delivery milestones and project finish date. It is therefore, important to review not just the critical tasks but also the non-critical tasks (with ‘float’) that can become critical as result of some change.
Detail Gantt View
You can access the view that displays the critical path via Views > More Views and applying the Detail Gantt View. See fig below.
(click picture to enlarge)
Gantt Chart Formatting Wizard
On the View menu, click Gantt Chart, and then click Gantt Chart Wizard on the Formatting toolbar or right clicking on the right hand side of the splitter bar and select ‘Gantt Chart Wizard’. Follow the instructions in the Gantt Chart Wizard to format the critical path as required.
Using Built-in Filter for Critical Tasks
The alternative to above is that you can apply the built-in project filter ‘Critical’.
Using Built-in Group for Critical Tasks
The alternative to above is that you can apply the built-in project Grouping for ‘Critical’.
Here is a really good video demonstration from Microsoft office online that you will find useful.
