Hi.
You can add the classes as described in the post you mentioned.
Go to Resources > Manage resources > Plugins > TinyMCE
Then go to the "Configuration" Tab and enter the class you wish to use (Advanced Image Styles).
If you want the styles to be visible inside the editor (not only your site), you need to specify a css file with the needed styles under Tools > Configuration > Interface & Features - "Path to CSS File"
Edit: Well.. i just tested this, sadly without the desired results. I don’t know the correct syntax for the Advanced Image Style parameter. Whatever i enter, i always get "undefined" as class.
But there is another option: Enter some selectors under Tools > Configuration > Interface & Features - "CSS selectors". You can then select the class from the "-Styles-" Dropdown in the Editor. This works fine.. the only drawback is that the class might be assigned not only to images. You can make the class only affect images by writing something like this in your css file though
img.classname {
...definition...
}