The Azure Subscription droplet is available on the droplets panel on the left-hand side of the designer view under Suggested droplets. You can also find it under the Management and Governance category, or alternatively, you can use the droplet search to locate it.
Once, you have placed your subscription droplet onto the drawing surface, you can then configure the properties of the subscription by opening the properties panel.
In the Subscription ID property, ensure you enter the correct subscription ID you wish to deploy resources into.
Alternatively, you can set this input to a parameter and supply the parameter value at deploy time using Cloud Maker Pipelines.
You can then deploy to your subscription either using direct deployments or Azure DevOps integration.