I recently bought one of these at a NNS. Another mum helped me set it up at the sale so I could check it worked. Brilliant, except I am trying it for the first time at home and can't fathom it. I can't get the sides to stay locked in place. Is anybody able to offer some useful tips? I know it'll be easy once I know how but getting started is proving to be a bit of a challenge! Thanking all you lovely mners in advance...