add code to
functions.php add image to toolbar

add_filter( 'wpforo_editor_settings', function( $settings ){
if ( empty( $settings['tinymce'] ) || ! is_array( $settings['tinymce'] ) )
$settings['tinymce'] = [];
$settings['plugins']             = 'compat3x,fullscreen,hr,paste,textcolor,lists,table,visualchars,charmap,anchor,image';
$settings['tinymce']['toolbar1'] = 'fontsizeselect,bold,italic,underline,strikethrough,forecolor,bullist,numlist,hr,link,unlink,blockquote,pre,wpf_spoil,undo,redo,pastetext,source_code,emoticons,fullscreen';
$settings['tinymce']['toolbar2'] = 'cut,subscript,superscript,alignleft,aligncenter,alignright,alignjustify,outdent,indent,removeformat,table,visualchars,formats,charmap,styleselect,anchor,image';
return $settings;
});