As Mary says, you have two options:
- configure the Atto toolbar as you want it; or
- switch to TinyMCE.
Obviously we'd rather you configured Atto as appropriate as TinyMCE is deprecated and will be removed in due course.
It sounds like you've found the Atto toolbar configuration page already so that's a good start.
At the top of that page, there's a list containing all of the plugins that you have available to you:
One of the columns is labelled 'Toolbar config' and the fields in this column are the ones you specify at the bottom.
If you read the help text underneath the textbox, you'll see it explains the format. Essentially though, it's:
groupname = plugin1name, plugin2name, plugin3name