I have stated time=pygame.time.get_ticks
then when bliting thing to the screen 
I try window.blit(time, (0,0))
but where the time is supposed to be it just says built in function.
Why is this??
Just to add a bit to furas answer.
Since this function is called get_ticks, you need to do the actual action to get the ticks.
There is one more thing that troubles me, you are trying to blit a integer to the screen, and this is not possible. 
What you need to do is create a surface from the string value of the miliseconds, and blit that.
Trouble with pygame.time.get_ticks