Compiling error "does not a type.."

i have to xompile the code but it was failed, what is the solution. i done to added the library thanks

sketch_jan02b:5: error: 'PulseSensorPlayground' does not name a type
sketch_jan02b.ino: In function 'void setup()':
sketch_jan02b:33: error: 'pulseSensor' was not declared in this scope
sketch_jan02b.ino: In function 'void getReadings()':
sketch_jan02b:133: error: 'pulseSensor' was not declared in this scope