The exception can be claimed with code 03 on line 2 of Form 5329. TurboTax does this automatically when you indicate in the questions following clicking the Continue button on the Your 1099-R Entries page the amount that qualifies for this exception by entering it in the Permanent disability box.
As for the supporting documentation, you can either provide the letter from your doctor if the IRS questions your use of this exception or you can include that letter and explanation with your mailed tax return.
