I would like to know how to give access to different users only with Author rights

Hi,

I have created this blog http://www.demosandpolis.com.

1) In this blog will participate 3-4 people, as they will write articles for the blog.

I would like to know if is possible to give access to them only as an Author (so only to connect to the Administration panel to publish their post and no more).

Is that posible? and if So, what I have to do?

2) For each user, I would like to create an Avatar. Is that posible? how I have to do it?

3) I would like to create a RSS channel for this website. Do you know what I have to do?

Thanks in advance for your help and support,

Virginia