As a new member over here, you must primarily get a permission to post in any of the section here in this site. After getting the permission you can easily understand the way on how o post by clicking on the respective tab. As for example in your case, after getting the permission you can go to Practice Test section, there click on Submit Questions, after that you would be re-directed to a page which is useful for posting your test question.
Initially for getting the permission in to this section, you are welcomed to read an article posted by our webmaster for to help the members like you, where you are intended to send your sample work primarily to the webmasters personal ID, then after they give you the permission based on your work.
For further details on this topic, please have a look at How to seek Posting rights for various section
Warm welcome to the website. The basics of the website has already been told to you by another helpful member. I would like to add something to it. Before you start contributing, read posting guidelines and help topics. They will help you to get familiar with the norms of the website. All the best. Hope you earn a lot from here.
'Do your Best and leave the Rest'