Imagemanager plugin doesn't show up in toolbar
The redactor toolbar can be configured in yourprojectfolder\config\redactor\ and you can choose the toolbar type when you configure your Field. By default, there is Standard.json file, where is the image toolbar button. For example, in menu Settings -> Fields create a new Field named Text, set Field Type to Redactor and now you can select in Redactor Config the Standard toolbar. I hope it helps.