please mark this thread as solved by clicking on the tick box below best answer!.
If you look at the partition guide, it shows you how to rid your PC of Windows but please start a new thread if you have any further questions.
Once you remove Windows, replace the Grub menu using Boot repair from Welcome > Installation Help > Dual Booting Boot > Boot Repair and follow the instructions, take your time!.. Start the Live CD and and open Welcome!.