turtle window not showing

[DT2000]

First you need to import the module, then after defining your code you need to allow it to execute.
See the code example below:

import turtle

def main():
    wn = turtle.Screen()
    alex = turtle.Turtle()
    alex.forward(150)
    alex.left(90)
    alex.forward(75)
    wn.exitonclick()
if __name__=='__main__':
    main()