Fugue Structure

Hello all I am new to this forum so bare with me,

I am just now playing around and reading up on composing my first fugue. Now these questions may sound silly but I am in need of some clarification.

While trying to follow a "Example of Key/Entry Structure, in a Three-Voice Baroque Fugue" which is evident in a wikipedia article I have seen linked around many times before, once my original invertible countersubject have been created for the initial voice how do I go about applying that to the 2nd voice which is either a 5th up or a 4th down from the subject in g minor?

For more clarification, if the same countersubject is being used for the 2nd voice how is it transposed to fit in correctly when the 3rd subject comes in.

Very sorry if this is redundant, but I am a little confused!

I'm not sure what you mean. Your subject should have already been written out and tested with your various countersubjects above, below and all around it before you start composing your fugue. You don't have to transpose the countersubject to "fit" because it will be in the same key as your subject and countersubject and already been worked out before hand to "fit".

If you need more clarification just ask.