How can I access my web site to make changes from a different computer? uccpilgrim.org?

I would like two other users to be able to add to or change the website. How can they do this without giving them my email address and login password? This site is for a church and the pastor and church secretary should have access.How can I access my web site to make changes from a different computer? uccpilgrim.org?
The only way someone other than you can make changes to a website is by giving them the ftp address along w/ login/password...its the only way to access it. They can use an ftp program (such as FTP navigator, or my fav FileZilla (mac or pc). But would need to know how to update/manage the site by editing the HTML files on their computer either through a WYSIWYG program like Dreamweaver, or simply by opening it up in a text editing software program like wordpad.