I don't think there is anything Forge specific here.
using controlnet really wants 10GB but this implementation works with 8GB at the cost of performance
Go to the Extensions tab, then Install from URL, use the URL for this repository.
Easiest way to ensure necessary versions are installed is to edit requirements_versions.txt
in the webUI folder.
diffusers>=0.30.0
accelerate>=0.26.0
Note
if noUnload is selected then models are kept in memory; otherwise reloaded for each run. The unload models button removes them from memory.