how; in what way; I wonder how
Emphatic expression used when the speaker is puzzled or frustrated about how something happened or should be done. Often implies 'I have no idea how' or 'no matter how I think about it'.
See also: どう
No matter where or how I search, I can't find it.
I have no idea how I messed up.
Combination of どこ (where) + を (object marker) + どう (how). The phrase literally means 'where and how', but is used idiomatically to express confusion about the method or process.