How can I post in Wordpress?

[Ken]

With Wordpress you need to be logged in to reply.

It depends how your teacher has set this up.
There could be a Forum page or simply a Blog type page.

Either way - log in ( user name and password ) then there will be a "Reply" button if it is a Forum
Hit this and a reply box should open.
Once you have posted you need to "Submit" the post.

If it is the Blog page then the reply box will be visible.
Post your "comment" then hit the "Post Comment" button

Hope this helps.