You can directly install pgAdmin in server mode by following instacution here.
Also for further information please refer to this link for server deployment and here is the file & supported parameter documentation which needs to be modified.
I installed PGAdmin web on a RHEL 7 server, however I am able to have only one user.
Found the below notes from pgadmin documentation, which configuration file do I modify.
Please help with any other information I need.
Configuration
What are Server Mode and Desktop Mode?
When deploying pgAdmin on a web server for multiple users, it is run in server mode (SERVER_MODE = True). This mode requires each user to have an account in pgAdmin, with their own password. Users are required to login to pgAdmin in order to use it. One or more users may be configured as an administrator and will be able to add or remove other users. For more information, please see the Server Deployment and User Management documentation.