You’ll have to add additional administrator seats for your account before you can invite others to be admins. If you scroll up, you can update your subscription and add additional admins for $10/month
Org members you add will only have access to neworks they create (the org owner will have access as well), or to the networks you specifically give them access to.
I added the new member and he has the capability to create new networks and also to manage other admin settings. so at the end is not possible to add a new member with no admin privilege.