you have two choices either remove the skylight and use a good silicone sealent on the inner flange of the collar on top of the roof then replace it and then silicone around the edge of the roof collar to ensure a good seal or if you want to then you can leave the skylight assembled and in situ and just silicone around the roof collar including any showing screwheads if there is any and also you could use roof and gutter sealent instead of silicone if you want to but that is usually black but it is really good stuff and the colour wont matter if you cant see it from the ground and if you have a poundland shop with 151 brand silicone or gutter sealent then dont be afraid to use either because i have a few times on my own skylight also other peoples and if your leak is coming through the handle rivets if you have any then simply plaster them with silicone..i hope this helps ....
dave james, April 2010
