To create a custom menu, go to Appearance > Menus in your WordPress admin area. Depending on the theme, there are could be a few menu locations, for example Primary Navigation, Mobile Navigation and Footer Navigation.
Plugins extend and expand the functionality of WordPress. You may automatically install plugins from the WordPress Plugin Directory or upload a plugin in .zip format via Plugins > Add New > Upload Plugin section.
Method 1: To upload the theme via WordPress admin area you need to use the installable zip file. Go to Appearance > Themes > Install Theme and click Upload. Select the yourtheme.zip file on your hard disk.