Good Captain,in your post of 8 Aug. you say "put a finger on the g string"-thats already occupied by my middle finger on the 2nd fret(A) in a D7 shape.
Surely you mean a finger on the D string 1st fret (E flat)? This gives the classic diminished shape that can be played right up the fingerboard on the top(thinner)4 strings.
I think it'll be a long time before a beginner needs a diminished chord-still,useful to know anyway.