You can copy an existing opportunity that is very similar to the new opportunity that you wish to create. Make sure the "Opportunities" tab is selected, select the opportunity that you wish to copy by clicking the check box in front of it, then click the "COPY" button in the column of buttons on the left side of your screen. You may also right-click on the profile you wish to copy, and select the "Copy" option that appears.
If the opportunity that you have selected has multiple or future schedule slots available you will see an option box pop up like this one:
If you wish to keep all future schedule slots for this new opportunity select "yes," and if not select "no." If there is only one occurrence (i.e., no schedule slots) for this opportunity, you will not see this option box. Instead, the opportunity will be copied and you will see a new occurrence tilted "Copy #1 of _____" with the same name as the original opportunity The new screen will look like this:
You can then go into the newly created opportunity and make any changes using the "Edit" button on the column at left just above the "Copy" button. The edit screen is the same as the "New" opportunity screen.