Hi Rachel,
You would need to do one of three things.
Change the language strings and make them blank. Here's a tutorial on language string overrides.
www.ostraining.com/blog/joomla/languge-manager/ You could edit the template for the module to hide those lines. But I'm guessing that might be more difficult than you need to get. If you really want to do that I'll try to give you some instructions.
So I would suggest looking for a custom login module on the JED.
extensions.joomla.org/search?q=login+module There are modules that will give you more control over the module through an interface.