Welcome to the forums, @BERP15.
If you are referring to this thread What is ERP Software?, you cannot post in it because it is almost three years old and the thread is closed.
Once you reach Trust Level 1, you will see an option to “Reply as New Topic”, which will enable you to start a related discussion.
I recommend reading the FAQs, and the articles linked to there, which will help you understand how the forums work.