Yes, you would file an amended to return to make any corrections on a return that is already filed. You should wait until the IRS has processed your current return that you have e-filed. How will you know this? If you are due a refund, you'll know it when the IRS sends you your refund check. Otherwise, wait about three weeks after your return is accepted by the IRS.
The amendment process is independent of the initial filing process. You should wait a little while (as noted above) to mail the amended return because you don't want it colliding with your initial return and confusing the IRS.
Note that amended returns take longer - the wait time for your additional refund (if any) can be 8+ weeks.
