In order to post a question or comment on an existing post within the community you will need to sign in or register for an account.
From the homepage click on "community"
The decide where you would like to post your question by clicking on the relevant heading:
Developers - API questions
Data users - all other data/services
Select "new post" and complete the information in the relevant boxes:
You will receive an email notification each time someone contributes to your post.
If you want to contribute to an existing post, simply select the question, post your comment in the empty box and select "submit"
To receive an email notification simply "follow" the post.