I need to know where to post my game introduction that I'm working on.

You can look at making a blog: https://www.gamedev.net/blogs/

If you have something you've released you can also look into: https://www.gamedev.net/projects/

and then there is the announcement section: https://www.gamedev.net/forums/forum/28-your-announcements/

I think blogs is what you're looking for.