You don't need to include an envelope addressed to yourself.
If you already have a Fedex account then you should have a Fedex account number. Most of the time when you set up an account with them, you need to use a credit card so that they have a way of charging you however it is okay if you don't, just as long as you give Fedex your address.
What I did was I mailed by regular mail to the FBI but on the form to request for my clearance there is a spot you can fill out your Fedex account number. If you want it returned to you using Fedex then you will fill in your account number on the form. They will then mail it back using your account number and will be shipped Fedex. This is what happened with me. I got my clearance back in 6 weeks when it was taking 12 weeks so I am sure this helped cut down on some time. I then picked up the clearance at Fedex and wasn't asked to pay for it then. They later sent us a bill. I believe it cost $37 dollars to ship it to us. It should arrive in one-two days.
I hope this helps you some. Also I would send at least 3 sets of fingerprints in with your request. This way they have more to work with. My first request I sent only one and waited 13 weeks to be told they were rejected. Also you may not have yours rejected but most first requests are so you should be prepared for that. Good news is though that even if they are rejected, they don't charge you $18 to try again and they process it faster. So I would just ship it either way you want to them but don't worry about shipping another envelope to them. If there is also not a place on the form to fill it out just write on a piece of paper the following and they will add it to your file.
1. Your full name
2. Home Address
3. Phone Number
4. Fedex Account Number
Then at the bottom say that you request them to ship it back to you using the following information and through Fedex then sign your signature. They will not accept the request this way without the signature. Make a copy for yourself then ship it with the form. Like I said I hope this helps you and others. Good luck.
P.S. Also just ship it how you would send any mail and to the address listed on their site.
