Flyscreen catch

The plastic catch that secures the flyscreen on our 05 Nuevo side windows (Seitz S5) has broken off.  I have sourced a replacement part, but am finding it difficult to work out how to fit it.  I naively assumed it would just clip in, but it seems it has to be slid in from the end on the blind.  How do I get to this? I have seen exploded parts diagrams but they don't help in understanding disassembly.