diy water leak from edges

[gaffyc]

Hi
Can someone link me to a DIY for fixing leaks coming in from the edge of the window.

It was heavily raining the other day and there was a lot of water leaking in, I checked to see if the window was up and it couldn't go up any further. I then opened the roof and closed it again and made sure all the trims were on the inside of the plastic deflector bit and still there was water coming in.

Not sure if it requires a reseal or if there is a way of sealing this then can someone let me know
thanks