Hi Vishwanath,
If it's TM, did you consider carrier collaboration portal which is mostly used by External Partners/Carriers/Vendors.
For EM WEBUI, you need the following settings/configurations.
For firewall: Check with Basis and Security or network admins on how to open it for external parties.
For Services, activate SICF services: default_host/sap/bc/webdynpro/saptrx/
For Authorizations, you need to configure the Authorizations in the following sections. The documentation has all the info to start with and what to configure.
Thanks,
Vishnu