The Arquillian plugin is listed in the Forge plugin repository so installation is trivial. In Forge type:
forge install-plugin arquillian
That's it! The plugin will be downloaded and installed.
Arquillian supports testing in multiple containers. This is done by using a Maven profile for each container. This makes it possible to have multiple containers configured side-by-side too. To add a new profile you use the arquillian setup command:
arquillian setup
This command will prompt which container to use. Remember that you can just re-run the arquillian setup command to install an additional container profile. For managed containers it might make sense to automatically download & install the container during the build to make installation on a build server more easy. This is only supported for AS7 at this moment.
Writing Arquillian tests is trivial, and is documented well: https://docs.jboss.org/author/display/ARQ/Reference+Guide
Forge can help you get started however.
arquillian create-test --class demo.CoolBean.java
Of course you can use the TAB key to navigate to the class that you want to test.
Arquillian uses the Shrinkwrap API to create micro deployments. A micro deployment is an actual package (e.g. war file). In some cases it's convenient to access those packages directly. You can do this by exporting a Deployment.
First navigate to the test class that you want to export, then use the arquillian export command to create the jar/war file.
cd src/test/java/demo/CoolBeanTest.java
arquillian export
Containers can be configured in arquillian.xml (hostnames, ports etc.). Forge can help you do so. Simply type:
arquillian configure-container --profile [maven-profile-id]
Forge will list all possible configuration options for that specific container. All you have to do is set a value.