Hi Ali, thank you for your question!
Social medias links are automatically converted into icons when you add menu items using the Custom Link option along with a valid social media URL. This guide from our support center (https://www.boldgrid.com/support/wordpress-tutorials/how-to-create-a-social-media-menu/) demonstrates how you can use the Custom Link option to add more links, such as LinkedIn, to your social media menu.
I hope that this information helps you get your menus designed as expected and please let us know if there is anything else that we can do to help!