I just got a new iMac for my home and totally confused how to use it and access the files, please help

Are you a Windows user switching to the Mac, or a brand-new computer user? Also, is this a brand-new iMac or an older, used model?

If you know Windows, the equivalent of Windows Explorer (the program you use to browse and find files) is called the Finder in Mac OS X. When you double-click on your hard drive (called by default Macintosh HD) it will bring up a file browser window. There, you'll see important destinations on the left: your desktop, Applications (programs - like the list of programs in the Start menu in Windows), Documents (files - like My Documents in Windows), and several other things. There are several icons for selecting how you display files: as a list, by icons, etc. Finder is really a sort of combination of Windows Explorer plus the Start menu in Windows. Of course, if you don't know Windows this paragraph probably doesn't make a lot of sense.

Here are some resources from the Apple Support site that may be helpful to you whether you are a brand new computer user or a Windows user switching:

iMac: New User's Guide (http://support.apple.com/kb/HT2054)
Mac 101: Get Started With The Mac (http://www.apple.com/support/mac101/)
Switch 101: Migrate to Mac (for Windows users) (http://www.apple.com/support/switch101/)

There are many other resources available, but those are some great freebies to get you started.