How to Scroll Windows on Your MacBook
Often, more stuff is in a document or more files are on your hard drive than you can see in the space available for a window. Just use the scroll bars that you see to move through the contents of the window — by default, scroll bars don’t appear until you move your pointer close to them. You can click the scroll box and drag it.
(For the uninitiated, that means clicking the darker portion of the bar and holding down your finger on the trackpad while you move your finger in the desired direction.) Alternatively, you can click in the empty area above or below the box to scroll pages one at a time.
If you’ve enabled two-finger scrolling in the Trackpad pane within System Preferences, you can scroll by dragging two fingers across the trackpad.
Depending on the type of application that you’re using, you might be able to scroll a window with your arrow keys as well — or perhaps use the Page Up and Page Down keys to move through a window.