I used put my little girl in our ocarro on the second click every so often. I’d do it for around 5/10 minutes and then lay her back down flat x
The occaro lies flat so I think it's okay to use from birth. I moved my little one into the big seat at 4 months as she looked fat too big for the carrycot and couldn't stretch out when sleeping!
My little one moved to the upright of the ocarro at 3 months. I just kept it on the second section. He now has it on the upright but still can’t sit unaided and it fine with the straps on. Hope that helps. X
My little girl hated laying down when she was 2 months old, you can get something that goes in the seat unit to support him if you was to sit him up