Is it possible to manage access to subsites from the mainsite using membership ONLY IN THE MAIN SITE

I´m configuring a develop site on gdmhome.co.
I have installed the single site with the plugin and everything work fine. Then I actived the Multisite option on the site and create the 1st subsite.
I Open the dashboard of the new site and there aren´t any user of the main site.
I like to manage all the permissions to the main site and the sub sites with Membership ONLY in the main site. Is it possible? I need only one login at the main site and access the subsite according to the level access on the main site and using the same credentials I mean the same user and password from the main site.

Thanks very much.

Camilo