By "software" do you mean an application? If so then simply locate the app and drag it to the Trash which is located in the lower right corner of the Dock. You can find the app in the Applications folder.
Once it is in the Trash it is not completely gone, it still resides in your folder. To empty the Trash click the Trash icon and select Empty Trash. This will fully erase everything that is located in the Trash.
BTW, if your iMac is less than 90 days old you have 90 days of complimentary AppleCare telephone support. If are not familiar with that please click http://www.apple.com/support/complimentary/