Board Thread:Support Requests - Getting Started/@comment-28687587-20170615235622/@comment-168424-20170616181751

So Classic RTE and VisualEditor are both "Preview Mode" editors, so the question is ambiguous. However, it seems you meant VisualEditor which is the default.

Like Tupka217 suggested, go to Special:Preferences, click the "Editing" tab, select a different Preferred editor: from the menu and click Save.