I am having difficulties following some steps of an answer to an existing question. Can I add my question to an existing question? If not, how can I get clarifications.
You can post a new question explaining you tried what described in an answer given to another question (with a link to that question, if it helps to understand better your question), and what exactly didn't work for you, the difference between what you obtained and what described in the answer, what you expected reading that answer, or what wanted to obtain.
Don't ask your question in an answer for the other question. Answers are for answering the question, and posting an answer to ask questions would cause the answer to be deleted.
Also, don't edit the question to add your question. Similarly, don't edit an answer to add your questions for the user who wrote the answer, or any other question you could have. Editing is not the alternative to commenting when you cannot comment, or asking new questions.