Start the Flash program. Click "New" from the File menu on the main Flash menu bar. Click the file type "Flash File(ActionScript 3.0)" from the New Document dialog box that appears. Click "OK" to close this dialog box.
Position your mouse cursor over the stage and press and release the "T" key on your keyboard to enable the text field tool. Click and drag your cursor to draw the TextField. Release your left mouse button when the TextField is the size you want.
Click the "Properties" option within the Window menu on the main Flash menu bar to display the Property Inspector. Select the "dynamic" TextField option from the TextField type list within the T section of the Property Inspector. Select the "multiline:" option from the Behaviors list box in the Paragraph section of the Property Inspector. If you don't select the TextField type as dynamic or the TextField paragraph behavior as multiline, the scrollbar will not work.
Click the "Components" option from the Window menu on the main Flash menu bar to open the components library. Click the "User Interface" option to display the components in the library. Position your mouse over the UIScrollBar option, then click and drag the scroll bar so that it is within the boundaries of the TextField you created. If you don't put the scroll bar in the TextField, the scrollbar won't attach or scroll. Release the left mouse button to attach the scroll bar to the TextField. Press the "V" key on your keyboard to enable the selection tool. Click the scroll bar to select the scroll bar and drag it so that it is aligned with the right side of the TextField.
Press and release the "T" key on your keyboard again to enable the text box tool. Position your mouse cursor within the TextField you created and type in several lines of text.
Click the "Test Movie" option from the Control menu on the main Flash menu bar to play your movie. Position your mouse cursor over the scroll bar and click in the scroll bar to scroll the text either up or down.