How to move wordpress?

I have a two sites. One is a regular html homepage and the other is a stock wordpress blog site in a sub folder. I want to get rid of the html site and replace it with the wordpress system. So what I thought i would do is download the database from cpanel, install the latest version of wordpress into the root folder for my site and then import the database into wordpress to recover all the posts and users. But everytime i try this, i get an error. The only way i can get it to work is to empty the database of the install then import the database from the other site, but when i do that, the page no longer displays. Like the site is gone. I don’t understand what is happening. Can you list the steps needed for this opporation?