Hi there darkblader,
Don’t despair. We’ll sort this.
(1) If you are talking about a wordpress.com blog then because you have admin status this means the way you post is the same way you do on your own wordpress.com blog after you log-in and submit your password.
To write a post, click “Write” then start writing in the large box.
To edit a post, click “Manage” and then “Posts” and then click “edit” for the post you need to change.
(2) If you are not talking about a wordpress.com blog then you have to go to Blogger or whatever other blog host the blog you have been made an “admin” on is located and get help from them on their support forum.