Login form

Hello, I want to create a login form on my pages.
I have a welcome image in the home page where what i want to happen is when i click on the image the other pages will be shown

http://i46.tinypic.com/wttvnk.jpg

I added different sets of users on the blog and I want them to login first before they can see the other pages & posts.

How do I do this? Thank You