What does automatic login do?
Instead of waiting for a user to enter their name and password, Windows uses the credentials you enter with Autologon, which are encrypted in the Registry, to log on the specified user automatically. Autologon is easy enough to use. Just run autologon.exe, fill in the dialog, and hit Enable.
How do I prevent different Users from logging into other devices?
First could be to include the user's IP address in your data (database, cache, token, etc). Then you could verify that the IP address of the first login is being used, and block all other login attempts or subsequent requests from any other IPs for the given user.