Yes thats one way to do it. see
Creating a site profile
The change the setting in options tab, click connect and it should work.
For future reference
(
Default sites) is a group, the group can be anything you want for e.g. create a group
named MY WORK SITES or FUN SITES, but it irrelevant as long as you can find the site you need easily.
FlashFXP has many default sites preconfigured what I used as example is from that list, but I could have used any list.
Let me know how it goes, though the error should go away, hopefully.