help with terminal disk utility setup OSX

This is very confusing so i apologize beforehand. I just bought a mac mini 2006 duel core model. I am trying to put OS10.6 thru a usb drive. I accidentally erased the original operating system. I am unable to use disk utility to partition the drive as it is greyed out. I am trying to use terminal to install from the usb drive. Somehow, when viewing on terminal the current hard drive got partitioned into several parts. When i try to install on the usb drive the setup on the disk ttys to place the software on a partition that doesn't have any space. Im not sure how this partition happened. Now, I would just like to erase the entire drive and not have the partitions so that I can have room to install the software. It seems that the only way to do this is thru Terminal. I am just not sure what the correct commands are. If anyone can help it is much appreciated!