See the samples on the Ór web-site:
http://www.orienteering.ie/or-home/or-samples
Format is:
Surname,First Name,Club,SI Number,SI Rent Request,Start Time,Entry Class,Course,Federation ID
The sample given there doesn't actually contain start-times, I just tested with start times and it sort of works...
So:
"Bloggs","Philip","BF",123456,"N",00:01,"M60L"," ",,0
"Bloggs","Helen","BF",654321,"N","00:09","W55L"," ",,0
Importing with Tools|Startlist|Import gives me the two starters, but the start times are:
24:01 and 24:09
I've no idea whether the extra 24 hours resolves itself. When I export the same start-list, I lose the 24 hours.