I went to myacca and then to the introduction in professionalism but I got stuck and couldn't move on.
Your browser might be the problem. Try upgrading your browser then try to access it again. It is pretty straightforward with short quizzes at the end of a module. The modules are also arranged serially so you must complete a preceding module before getting access to the next module. If i can remember correctly and if it has not been changed, there is a quiz at the end that you must score greater than 50 on.
If you think this issue is due to a technical difficulty contact ACCA. They can guide you in the best way possible.
Other than that there are different modules and you must finish one to get to the next one. In the end you'll have to solve a case study which will basically be you answering a set of multiple choice questions to solve ethical dilemmas and reaching a final decision.
Best of Luck.