Gas Bottles

Hi..we only started caravanning last year and are very "green".

We went away for the first time this year on Monday to iron out a few creases in our experience, however we have a problem in that we have not used the gas yet. I bought a new cylinder and went about fitting it...all well until I attempted to fit the gas pipe to the van. I couldn't get the rubber pipe to go onto the inlet pipe on the van...any tips greatly accepted..Thanks Hilary and Craig