I bought one ages ago but I've hardly ever used it. All that's needed to get one up and running is to buy and insert an SD card (or micro-SD card, as appropriate for the model, unless one comes supplied with the unit), attach it to the windscreen (or possibly to the dashboard with some models) and plug the lead into cigarette lighter socket.
However I found that getting the thing to stick to the windscreen, without it falling off after a few miles, wasn't as easy as it was meant to be and that I couldn't find a neat way of routing the cable between the dashcam and the power socket so that it wasn't dangling in front of me as I was driving.
Perhaps I ought to give it another try though.