Hi, I am not fully sure I understand your question, but if you have a new elementary flow to add to your system, then
1, check if this is really needed (and the database and method and impact category you plan to use does not already contain one that fits)
2, create the flow
3, add it to the impact category or categories you want, with the characterisation factor
4, add the flow to the processes where it fits.
Does this cover your question?
All the best,
Andreas