The unused credit from 2009 is carried over to line 6 of Form 3800, just as you thought. Then from line 6 to line 8. Then you will need to complete Part II of Form 3800 to determine what portion of the credit carryover is allowed for 2010. Once you get to line 32 of Form 3800, this amount flows to line 53 of your 1040 and you mark the box for the 3800. If you need further assistance with this issue, please let me know.