I have downloaded the Option Strategy Builder software, but I am not able to make any inputs. Do I need to have an Ameritrade account to download the option chains?
You could try, but the official website appears to be discontinued. If the login process is done through that website, then creating an account on Ameritrade would be useless, but you can try since the Ameritrade website is still online. Access the below and create an account to use in the application.
For trading-related applications, it's a must to log-in to the official servers in order to obtain the necessary data.