Do you already have a WordPress install or do you need help on how to install it?
If you already have it, do you need help on how to make a post in an existing theme, or do you need help on how to create a theme from scratch?
If you would like to make a post in your WordPress site go to http://www.yourdomain.com/wp-admin from there on the top left there is something that says “post” click on the and you should be able to make a post.
Not something we could just lay out quickly here, and especially since you said have little experience in WordPress, you’ll need to know about a lot of other WordPress things before you dive into creating your own themes. I definitely recommend reading a proper tutorial for everything, and @ChrisCoyier’s book Digging Into WordPress is an excellent resource for that.