Add Search To Menu plugin allows you to add search form in your site navigation bar that makes users to search your site easily.
The plugin provides you various settings in the admin area which you can use to customize the search form. The plugin is easy to use and you can configure it using the plugin settings from Admin Area -> Settings -> WP Home Page Menu
The styling of search form highly depends on how the theme styles search form so if you face any styling issue with it then to style it correctly feel free to get free support from our support forum.
The plugin options are self-explanatory but if you have any question related to WP Home Page Menu plugin then please ask it in the plugin support forum here Add Search To Menu.