Alright, my best thing I could do is to make friends on youtube/facebook, and then share your forum.
Is there an easier way?
Twitter's a great option.
Way, way too much to explain in one post tbh. Sorry, there is limitless possibilities. I made my first forum with no help when I was 12. It got no members for like 2 months, but thought of a very unique idea (which was to record people's halo 3 videos with a capture card for free) and then activity was born.