Hi @Yunyi1989 ,
You cannot add users to an UAG appliance. The UAG is a proxy for your Horizon Connection servers, so all settings must be done on the connection servers.
To restrict certain users from using Horizon from outside your network, you can specify "external users" (or a group) on your Horizon Conneciton servers (Users and Groups - Remote Access). Only those users will be allowed access through the UAG, while other users will still be able to connect to Horizon internally. If no users/groups are specified on the Remote Access page, any entitled user can login remotely.
Hi @Yunyi1989,
You can manage remote access via the Horizon Console:
Exactly what @Mickeybyte says:)