Migrating content from older custom CMS
If you know any php I recommend the Migrate module to easily write a SELECT title, body FROM old_content and map them to Title and Body fields of a Drupal Page type. You would do this with a Migration class. See documentation on the project page.

You could also try the Feeds project.

There are modules for Migrate to migrate from Wordpress or older Drupal sites. You could use that as example migrations to move content, menus, etc into a new drupal site.

I've migrated pages, and custom Joomla content for courses and instructor content into Drupal content types .... but every migration use-case is always unique; I'm just recommending tools I've used.