Follow the instructions on ibm-blockchain.github.io to launch a basic IBM Blockchain network on the IBM Container Service's free plan. At the end of the install, you will be able to obtain a public URL to access your instance of Composer Playground (the UI for creating and deploying Business Networks to Fabric).
There is a single script install available as well as full documentation on individual commands for custom installations.
You will need to clone this repository to get the relevant bash scripts and YAML files.