update registrar docs on how to build the server with docker

Author: Eslam-Nawara

node-registrar/Makefile

@@ -1,7 +1,7 @@
 run:
 	go run cmds/main.go --postgres-host localhost --postgres-port 5432 --postgres-db postgres --postgres-user postgres --postgres-password password --domain localhost --server-port 8080
 
-postgres:
+start-postgres:
 	docker run --name postgres -e POSTGRES_USER=postgres -e POSTGRES_PASSWORD=password -e POSTGRES_DB=postgres -p 5432:5432 -d postgres
 
 stop-postgres:

node-registrar/README.md

@@ -81,11 +81,11 @@ Replace `<domain>` and `<port>` with the appropriate values.
 
 ## How to run the server with docker
 
-1. use the docker file to build the docker image
+1. To use the docker file to build the docker image, run this command in the root directory of the sdk
 
-   ```bash
-   docker build -t registrar:latest .
-   ```
+```bash
+docker build -t myserver:latest -f node-registrar/Dockerfile .
+```
 
 2. run the image