Add how to use constraints once we created node labels (#2964)

* Add how to use constraints once we created node labels

* Fixes as asked by @joaofnfernandes

datacenter/ucp/2.1/guides/admin/configure/add-labels-to-cluster-nodes.md

@@ -17,9 +17,6 @@ lifecycle, or the hardware resources they have.
 
 ![](../../images/add-labels-to-cluster-nodes-1.svg)
 
-In this example, when users deploy a service they can add constraints for the
-service to be scheduled on nodes that have an SSD storage.
-
 ## Apply labels to a node
 
 Log in with administrator credentials in the **UCP web UI**, navigate to the
@@ -37,6 +34,30 @@ You can also do this from the CLI by running:
 docker node update --label-add <key>=<value> <node-id>
 ```
 
+## Add constraint to a service
+
+When deploying a service, you can specify constraints, so that the service only
+gets scheduled on a node that has a label that fulfills all the constraints
+you specify.
+
+In this example, when users deploy a service they can add constraints for the
+service to be scheduled on nodes that have an SSD storage.
+
+You can add deployment constraints to your docker-stack.yml file or when you are creating a stack:
+![](../../images/use-contraints-in-stack-deployement.png)
+
+Or you can apply them when you are creating a service.
+
+![](../../images/add-constraint-to-service.png)
+
+You can check if a service have deployment constraints, navigate to the **Services** page,
+and choose the service your want to check.
+Once you're done, click **Scheduling**.
+
+![](../../images/check-contraints.png)
+
+From here, you can add or remove deployment constraint too.
+
 ## Where to go next
 
 * [Store logs in an external system](store-logs-in-an-external-system.md)