Cytisus Lena.

Hello everyone, I really need some help please. I recently bought a cytisus Lena which I have only found out I should prune.🙁 I haven’t got a clue how to do that. There are no flowers left on it, just pod shaped “things”. Reading that I mustn’t cut into old wood has worried me as I can’t tell the old from new. Help 😧😧