I have not taken it (still in residency), but according to my recent seniors who just graduated and sat for it, you take it at home remotely on your own computer (not sure about the specific setup or any special software or anything). No need for any extra preparation besides what you should have already been doing in residency — meaning your regular Cheng Ching and regular Qbanks (combank or NYKN, etc.). It’s not really that osteopathically different besides maybe 1 or 2 OMM questions here and there which won’t make or break your chance at passing it. There is a reason pass rates are higher than the MD boards to begin with.