windshield leak

You can try the silicone thing, but I haven't had much luck with it as it doesn't bond good to the existing windshield adhesive.
To fix it right, you need to pop the windshield out and clean it up and use new windshield adhesive. You should be able to get it out without breaking it. Last one I had replaced, two guys sat low in the seat and used there feet/legs to pop it out.

 

silicone is not the good thing. use something with polyurethan, like Polish Crocodile.

Clean surface with solvent for pain before U apply seelant

 

I'm not a fan of sealants around windshield seals but, sometimes the the body gets bad enough that new seals won't work without bodywork. In these situations i use a sealant made by 3m thats called window weld. It's poly based and somewhat flexible. Once applied and setup, you have to cut it out. It's that good. Hope this helps.