Update use-a-web-proxy.md (#6678)

ee/dtr/admin/configure/use-a-web-proxy.md

@@ -28,6 +28,18 @@ To confirm how DTR is configured, check the **Settings** page on the web UI.
 
 ![DTR settings](../../images/use-a-web-proxy-1.png){: .with-border}
 
+If by chance the web proxy requires authentication you can submit the username
+and password, in the command, as shown below: 
+
+```bash
+docker run -it --rm \
+  {{ page.dtr_org }}/{{ page.dtr_repo }}:{{ page.dtr_version }} reconfigure \
+  --http-proxy username:password@<domain>:<port> \
+  --https-proxy username:password@<doman>:<port> \
+  --ucp-insecure-tls
+```
+NOTE: DTR will hide the password portion of the URL, when it is displayed in the DTR UI.
+
 ## Where to go next
 
 - [Configure garbage collection](garbage-collection.md)