OpenDNS does not and cannot filter users or devices. A service in the cloud has no access to such internal information. OpenDNS as DNS service knows about domains only which are being looked up by networking programs within your networks.
As a first step you configure the OpenDNS resolver (= DNS server) addresses on your routers.
As next, for each public IP address you're working from you must manage a separate OpenDNS dashboard network. If you cannot create additional networks in your account, raise a support ticket to get more. Alternatively, create additional accounts with one dashboard network each.
https://dashboard.opendns.com/settings/
"We have three different locations with multiple users at each location."
OpenDNS is for home use exclusively. It sounds you're looking for a solution in a corporate environment? Then Umbrella is the solution: https://umbrella.cisco.com/products/packages
What I said above about OpenDNS is in principle valid also for Umbrella.
"I have no idea what I’m doing."
This sounds dangerous...
