Article: This tab should be in your Mac's menu bar at the top of the screen. If you don't see Go, click the desktop or open a new Finder window to make it appear. It's at the bottom of the Go drop-down menu. This icon resembles a Mac hard drive with a stethoscope on it. Doing so will open the Disk Utility program. Click your Mac's hard drive in the upper-left side of the Disk Utility window, just below the "Internal" heading. This tab is at the top of the Disk Utility window. It's below the pie chart. Doing so won't immediately delete the partition, but it will allow you to make changes to the system drive. Click the piece of the pie chart that represents your Mac's system. It will usually be on the right side. Click the "Size" field, then type in a new size in gigabytes for your Mac's system drive. For example: if your Mac's system drive is 250 gigabytes and the partition is 250 gigabytes, typing 400 into the "Size" field will set your Mac's drive size at 400 gigabytes, leaving 100 gigabytes for the resized partition. This option is in the bottom-right corner of the window. Doing so will begin extending the Mac's system drive and resizing your selected partition. This will complete the extending process. Your Mac's main hard drive partition should now be resized.

What is a summary?
Click Go. Click Utilities. Double-click Disk Utility. Select your hard drive. Click Partition. Click -. Select the system drive partition. Enter a new size. Click Apply. Click Done when prompted.