Need help with Krippendorf's Alpha for calculating inter rater reliability

I am a plastic surgeon and am doing clinical research. I have 46 patients who underwent a cleft lip technique by me. I had a team of four raters (judges) rate the results 1-5 (1=poor, 5=excellent). I would like to use Krippendorf's Alpha test to calculate inter-rater reliability. Can anyone help me on how to do this? Thanks