Change the width of each bar

Hi there, Im now having lots of trouble on trying to find out how to decrease the width of each bar. I'm currently using a mac, I've searching for lots of solutions such as the 'Decrease Layout Stretch', but it doesn't work. I have a piece with lots of note in a bar, now I have only one bar a line which means I need to have more than 5 pages with only 5 bars in it.
Please give me a solution, I'm waiting for it desperatly