You can use two methods for checking out files:
Select the file(s) you want to check out from the main window display. Then, choose Commands > Check Out.
A check mark is displayed in the file icon(s) of the selected file(s). This method is valuable when you want to check out several files at once.
Double click a file icon in the main window.
A check mark is displayed in the file icon and the file is checked out with you as the owner. This is not the default behavior. To enable this double-click action, you must change the default behavior by Choosing View > Options, selecting the Toggle SCCS State radio button in the Double Click Action section of the Options dialog box, and then selecting the Confirm Double Click Check Out checkbox (see "Changing Versioning Properties").