Can it be added to an existing game or do you have to start from scratch?

Can be added to an existing game, just clear a small area around the starting point cause ti will spawn a wreckage there

I have added your mod to an existing game but it does not seem to spawn the starting Tesseract.

That is weird! Do you have buildings at the starting point? Maybe you deconstructed it with bots and the tesseract is lost in your logistic network? If none of these options you may have to use a command to give yourself the tesseract : '/c game.player.insert("CW-tesseract")' but this will deactivate achievements.

Thanks for update. I have searched the whole area roughly where my spawn point was and can't find in the logistics system so bots have not picked it up.
I will try a new game and try it there.

Quick update, reloaded into existing game and found it.
Not sure if it was just me not finding it first try, but it does not destroy buildings already placed so was a little hard to find.
Idea would be, if it had destroyed the buildings or possibly have it show icon on the map so you can find it.