After replacing battery engines does not turn over

So the battery kept going flat, I changed the battery, ever since the car won’t turn over, all of the electrics come on and then I turn the key to start the ignition and everything cuts off, I get nothing.
A few lights come up on the dash but then they change pretty much every time I turn it on, I mainly get the lightning bolt in the circle with a spanner underneath. It’s got an electric handbrake, which I think that it what that like is about. Really ain’t got a clue.