Software need to be installed for completing Appian Foundation course

Hi curiois,
Appian is not a "designer" or just "piece of software".
Appian is a lowCode platform. You can develop and run applications "on" that platform.

here you can get your own appian instance. Called "My Community Edition Site"
https://community.appian.com/p/my-learning-journey
for free

kind regards,
Richard

Appian is a web-based software so you don't need to download or install anything. Once an environment is configured with Appian (either on-premise or on the cloud) you can access from any web browser. Like Richard said, if you're just getting started I recommend using Appian Community Edition which is hosted in Appian Cloud.