After installing otk you'll probably want to start using it. If you've followed the installation instructions for a source checkout you'll have an examples directory available. You can compile one of the examples like so:
€ OTK_EXTERNAL_PATH="./external" otk compile example/centos/centos-9-x86_64-minimal-raw.yaml
# ...
Note that this example will take some time to generate, this is due to dependency solving. After the command is done it will output the generated content on STDOUT.