ahild, welcome to FT!

Sorry you had such trouble using your vouchers. Hopefully you can learn about them on ft. Did you do "tickets by mail"? There is a thread on that, if you search for it. I've successfully done several tickets by mail.

Another alternative is to ticket at the airport. Both of these options are good if you have paper vouchers.

If you have electronic vouchers, you can redeem them on-line at UAL.com. No need to send anything.