The graphic styles are a powerful addition to Illustrator combining effects as well as patterns and fills and strokes, all the are in standard AI format.
Go to the right side of the styles panel (found in the window menu). Select the open library menu command and browse for the set via the other libraries menu command.
You don't have to browse for them, you can find them in the list such as 3D effects, additive, artistic effects etc. Add your AI files to the presets folder which can be found beneath the application itself (which can be found in the program files folder on the PC and applications on the mac). You will also see an en_GB or en_US etc and then all the folders. If you click on that folder you will see all the image effects, type effects etc in AI format. Add your files to that folder. You may need admin privilege to add them to that folder. Once they are located there, you will be able to access them via the list.
You can also access them via the window menu right at the bottom with the brush libraries, symbol libraries etc.
You can also access the items via the same structure via any panels opened for the libraries such as the type effects, image effects etc. You can go to the bottom of the panel to the menu and expand out to see all the library names. The next two buttons enable you to scroll through the libraries as long as they are located in the presets section.
Select a path and click one of the presets and that will be added to the document's presets for that type and will be stored when you save the document as an AI file.