I think I solved it!
I found a thread on reddit from 2 years ago: https://www.reddit.com/r/Minecraft/comments/34bxus/installing_forge_with_the_new_local_java_runtime/
I followed his instructions about the console commands and it worked. Forge is installed now and I could follow the rest of @paintbrush11's explanations!
I share this for those who also have a local jre and didn't solve the issue yet.