The WebUI needs to know the address, port and HTTP protocol used by BAM. These are set here WebAPI Configuration Options
Now simply point your web browser at the URL for the BAM WebUI and it will interact with your BAM installation. If the WebUI does not load up, or you cannot sign in using it, please refer to the problem determination here Web UI.
It is recommended that you change the admin password when you first login. To do this, hover over the "Welcome admin" text at the top right of the screen and click "My Profile". Then click on the "Change password" button.
Security considerations for the WebUI are described here Web UI.