If you already e-filed and received your refund, you cannot "file again." What you need to do is prepare an amended return to make any additions or corrections to your tax return.
A 1040X cannot be e-filed. It must be printed and mailed. It will take about 3-4 months for the IRS to process an amended return. It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.
Wait about 3 weeks from mailing and you can check the status of your amended return: