Did mine many years ago.
From memory the metal strip on the offside (were it hinges) goes on the inside.
The rest are on the outside.
Use Polyurethane sealant as doesn't contain salt etc.
Also, don't seal the plastic/metal to the top - when you get it close to being fitted on the bottom, you are supposed to take up any slack by undoing the the top strips and pulling taught (something like that....)
Like I said, must be 8 years since I did mine.
Hope it helps.