Import aperture library to iPhoto

You don't, simply.

If you have the latest versions of both apps then iPhoto can simply open the Aperture Library.

how do I import Aperture Library into iPhoto library?

If you want to merge two libraries by importing an Aperture library into an iPhoto Library, open the iPhoto Library in Aperture and use the command "File > Import > Library" to import the Aperture library into the iPhoto Library.

See this document: Aperture 3.3: How to use Aperture to merge iPhoto libraries

My entire photo library is an Aperture library. When I open it in iPhoto how then can I save it as only an iPhoto Library? I understand Aperture will no longer be a viable app in the future.

There is no difference between an iPhoto Library and an Aperture Library. Both applications are using the same format for the library since iPhoto 9.3 and Aperture 3.3.

See: Aperture 3.3: Using a unified photo library with iPhoto and Aperture

If you want to switch to iPhoto alone, simply continue to use the library with iPhoto.

Both applications, iPhoto and Aperture will no longer be developed by Apple. Apple announced that neither iPhoto nor Aperture will be sold any longer at the AppStore after the public release of MacOS X 10.10.3. So the future support for iPhoto and Aperture will be the same.

But both Aperture and iPhoto will work with Yosemite, and probably future system versions. Only, there will be no longer any new features added.

Also, i'm using the beta version of Photos. It imported my iCloud photos perfectly but not the Aperture Library. Do you know how that would be accomplished?

Thanks! Really appreciate the assistance!

You do not import an Aperture library to Photos, you ctrl-click the Aperture Library and select "Open with Photos" from the contextual menu.

Or hold down the alt/options key while launching Photos. Then select your Aperture library from the Library Chooser panel.

But make a backup copy of the library, before you try it. Just to be on the safe side.