All plugins that you list in the textarea on the left (one plugin slug* per line), will be added to your customized boilerplate.
After installing the customized boilerplate in your WordPress installation all required plugins will be downloaded from the WordPress repository and activated.
* A slug is the unique identifier of a WordPress plugin. You can visit any plugin in the WordPress repository and get it’s slug by copying the last part of it’s url.
The slug for the Jetpack plugin, which can be found at https://wordpress.org/plugins/jetpack/, would therefore be jetpack.