Multisite – Users Have Access to all sites

I’m looking for the best method to get all users to be able to use / login to all sites on my network. I understood this plugin had that function. My multisite is all part of one store with different stores / sites for areas in the city. I want a user who has an account in the system to be able to login to all sites. Please advise if this is doable or if i’ve misunderstood the plugin.