The clutch controls shifting the gears, which is usually done for you by an automatic vehicle.
The shifter is usually in the center console area, it is a stick which lines and numbers on the knob of it. This is used to perform the gear shifting
The emergency brake, is in all vehicles but in a manual vehicle it can be considered the vehicles park option. It should always be activated when the vehicle is off or when you want the vehicle to stay without pressing the main brake.
The RPM gauge, rotations per minute gauge, is how fast the vehicle engine is going based on the gear. This will be used to know when to switch between gears.
Make sure the vehicle is in neutral (no gear engaged), this can be checked using the shifter:
Wiggle the shifter left to right, if it has a lot of freedom to move then the vehicle is in neutral. Test this when the vehicle is in a gear to feel the difference - push the clutch all the way to the floor and hold it there, then move the shifter to a gear and wiggle it left to right, notice how it does not move as much when not in neutral. It is important to hold the clutch down all the way throughout the test.
Now that the vehicle is in neutral, push the clutch all the way down to the floor, hold the brake down, and turn the ignition. Note: If the clutch is not pushed all the way down, the vehicle won't start.
You can now let the clutch go as long as the vehicle is still in neutral