Short answer: no.
Longer answer: If you're on the free version of WordPress.com58, they don't allow you to install plugins, so you'll need to use embed codes to add your ConvertKit forms to your site (see this article71). If you upgrade to a paid plan on WordPress.com58 you'll be able to use the plugin as well. If your WordPress site is hosted anywhere other than WordPress.com58 (for example, at WP Engine, SiteGround, Bluehost, GoDaddy, etc) then you should be able to install plugins as well as use the embed codes.