When you say 'my hard drive', can I take it that your machine only has the one drive?
And what do you mean by 'wipe'? If you mean erase the drive completely, this is not ideally a task for Eraser, which cannot (obviously) erase the very operating system on which it is running. For that, the standard tool is Darik's Boot and Nuke (DBAN), which comes as a drive image that you burn to CD ROM; the machine is booted from the CD, and DBAN erases every drive it can find - it's not called 'boot and nuke' for nothing. DBAN has a companion forum to this one, from which you will get download links and some information. But, for such a brutal program, it is not particularly well documented and is not currently supported. If your technical knowledge is limited, you may need to look elsewhere, and Eraser can help.
I agree that Eraser's task pane, though neat and tidy, does not reveal its secrets easily to new users. If you click on 'Help', a PDF manual opens, which explains things pretty clearly. If all you want to do is erase files and folders, you will find that the context menu in Explorer has an Eraser context menu item that you can use to erase selected files and folders. A second method is to move files to the Recycle Bin as normal, then use the Eraser context menu item to erase the contents of the Bin. Yet another method (particularly suitable for erasing tasks you will do more than once) is to create, and then run, a task in the Task pane; right click on the pane select New task (or just press Ctrl+N), and a reasonably clear task dialogue appears; press the add data button to add items you want to erase to the task. You can include multiple items for erasure in a single task. Once the task has been saved, you right-click on it in the pane to run it. I hope that, in conjunction with the manual, this is enough of an introduction to the program.
As I do not know what your specific task is, I hope the following example will illustrate how Eraser can help you. Suppose you have a laptop that you want to dispose of in basic working order. This laptop comes (as many do) with a recovery partition, and a recovery program which formats the hard drive and restores the machine to factory condition. You can use Eraser to destroy all the personal data on the machine that you can identify. Then run the recovery program; the machine is now in factory condition. Reinstall Eraser, and use it to wipe all the free space on the hard drive. If you like, install and run a file recovery program such as Recuva, and use it to check that there is no recoverable user data on the drive.
I hope this helps. If you want more help with your specific task, do come back.