First Project: LEDs

I just started using Arduino but every time I make a project it creates errors that I dont know how to fix.
Here's my sketch.

if (SwitchState == LOW) {

digitalWrite(3, HIGH);
digitalWrite(4, LOW);
digitalWrite(5, LOW);


digitalWrite(3, LOW);
digitalWrite(4, LOW);
digitalWrite(5, HIGH);

digitalWrite(4, HIGH);
digitalWrite(5, LOW);


Go have a look at some of the example sketches. You have to have your code in functions. Two functions, setup and loop MUST be defined for your sketch. Again, go look at some of the examples and you'll see how this stuff is supposed to be laid out.

Yes, you're missing the beginning, and end, which can be inferred to be:

byte switchPin = 2;
byte switchState;
void setup(){
pinMode (3, OUTPUT);
pinMode (4, OUTPUT);
pinMode (5, OUTPUT);
pinMode (switchPin, INPUT_PULLUP);
void loop(){
switchState = digitalRead (switchPin);
// then your code

} // end of loop()

check upper/lower case consistency in naming also.
SwitchState is a different variable than switchState, so you need to make those match.