Would it be possible to do so here?
I can only suppose that as long as a person is here for other reasons as well it might be okay? I’ve just joined under pretty much the same pretenses actually, and that is to get word out for my Oekaki RP board. But I have a feeling I may stick around here just for the topics!
Generally, advertising is definitely a no-no anywhere in the forums, however, you are allowed to advertise a website in your sig, as long as the link isn’t for something like MMO gold selling or hawking penile enhancements, nor is outright offensive, overpowering or otherwise annoying or obnoxious. As I’m only a moderator you might need to get an admin like Jessie or Marceline to clarify the details of that though.
If there’s a site you like and you want to advertise it, you are permitted to drop a link to it in your posts, as long as it’s relevant to the subject.
And, as has been mentioned, any posts made by new members which feature any kind of web link within them are automatically moderated to stop spam. This restriction is removed once you reach a certain number of posts however (from what I’m aware it’s between 5-10 posts needed).