To install the hook, simply visit your admin and go to Settings->Hooks, then click on Add New and type in wordpress-import, and click install.

Next visit: /admin/wordpress-import and you will see a screen that looks like the following:

Simply, click to choose your Wordpress XML file, select a few options and click Import

And now you will have your Wordpress Posts, Pages, Categories, and Users migrated over to your database.

Before doing your import you may also wish to change the body column in your post table from a type of text to be longtext it just depends on the length of some of your articles. In some imports this can cause an issue if it has not been changed.