no i am playing the 1989 season, joining the lotus judd team as teammate of piquet

i reached the final and i'd like to make it as real as possible, so i need a wet race.
in section editors i found the "GPWet32" Editor, but it doesnt work. (think its my fault, because i don't know how to install that it works.
can somebody explain it to me step by step and for guys like me, who doesn't are perfect in english language?
i tried the readme, but i think i do something wrong, cause it doesn't work..
thanks

best regards from dortmund germany
Roman