So you added water to your carboy, and then went to add the wort? But then you still had concentrated wort left.
1. Carboys aren't exact, next time measure out where the 5 gallon mark is.
2. I would dump some of what is in the carboy into a sanatized container. Then add the rest of the wort, and then add the diluted stuff back in.
3. Your going to need a blow off tube if you have your craboy that full. I think a lot of people only put 5 gallon in a 6.5 gallon carboy for primary fermentation. I just use a bucket.
Good luck.