How can an administrator allow an org to publish a change set to another org?

In the target org: Open Deployment Settings, Select the environments to allow publishing from and Move themto the Enabled list

In the source org: open Deployment settings, Select the environments to publish to and Move them to the enabled list

In the source org: Open Publish Settings, Select the checkbox next to the environment to publish to and Click Save

In the target org: Open Deployment Settings, Click Edit next to the source org. Select Allow Inbound Changes and Click Save