Hi @Shashank S,
Adapted from this answer by @Jacob Gillespie:
Make sure the client you're connecting from is on the same local area network as the computer running FlexSim's webserver. Then connect using the local IP address of the machine running the webserver. You must also use the port that is configured in your flexsim webserver configuration.txt file. By default this is port 80, which is the standard port for http.
For instance, if the local IP address of your FlexSim webserver is 192.168.1.14, and it was serving over port 80, then in your client browser you would go to the url http://192.168.1.14. If you were serving using the custom port 8123, you would add the port number at the end, like this: http://192.168.1.14:8123.
If your webserver is running on a machine with a global IP address then you could connect to it over the internet using the global IP address.
In either case you may need to add firewall exceptions to your webserver system.
Be sure that the file paths and other configurations are set correctly in your flexsim webserver configuration.txt file.
See the webserver documentation for other details.