Once an app deployment is ready to go (Distribution is complete and deployment has been created) you can force a client to install said update using the steps below.
All of the steps below can be monitored by viewing the logs on the clients located in C:\Windows\CCM\Logs
1. In Assets and Compliance, find the device(s), right click, Client Notification, Download Computer Policy.
2. After waiting around 30 seconds or so, click Evaluate Application Deployments