problem with time line
 

hi guys i have a problem with the limeline i can't enlarge it.
it stands now from 1 to 24 and i want it to go to 48 but how must i do that ?
please help me
this is my first work

the white box next to the time line contains which is the last frame in the current time line. you can change that to any value. also, the box next to that one alters the total amount of frames in the timeline. you can change that value and then move the time slider (below the timeline) to get to different frames...