Talk about SEO for forum

[guest14546]

I've got a website and I open a forum (sub domain)  as a channel to attract more visitors to increase revenue
However, it seems quite hard to do this mission. The keywords are not appeared on Google. Google doesn't seem to like forums very much? or Google does not prioritize forums on Google Search? I don't know why
Or am I going into the wrong way? I am missing  SEO methods

Can anyone help me answer it? Thank you so much