If you do not have FTP software, then google "free FTP" and download a program (I use WS-FTP, which is not free, but has a 30 day free trial - the Home version should do it and is very easy and clear). Core Lite is free, but I don't love it. Moderator Note: We like to recommend FileZilla: http://filezilla.sf.net
When you set up your FTP software you will need to provide ftp information when you configure, so you can connect and upload files to your site. That will be something like ftp.mysite.com You will also need the password. If you don't know your password,contact the helpdesk of your hosting company.
The FTP software will look very similar to Windows Explorer (assuming your on a PC platform here), and have two windows - one with your local (PC) view (usually on the left) ,and one with your files on your host (usually on the right).
You will also eventually need a decent .php editor (notepad works in a pinch, but I prefer Note Tab Lite - free - look online.)
That should get you started.
~Laura
Laura M Collins Invitation Designs
"The best way to navigate in a new area is to first get totally lost in it."...Mike L. Stein