It really just happens naturally if you use their name when you talk to them just like it does with a child. I've never had to do anything special. But if you have trouble I agree with the above advice from Deana. My cat and my dog both answered to multiple names too. Animals are smart.
Hi bryanarana96, Dogs pick up on their names pretty fast, but you should use the name EVERY time you talk to the dog for the first month or so until they have it down and understand that that word means them.. Say his/her name and hand her a treat, say the name repeatedly when calling them, and when they come praise them a lot, again saying the name (ie 'daisy, come, come daisy, yes daisy come!.... Oh good dog daisy, good girl daisy!) Also until they get used to one name don't add nick names or cutesy versions... my dog will actually answer to 2 names and the combination of the 2, but I made sure he knew the name I would call him by the most first. (Tanner... then the cute version Tanneroo and he answers to plain Roo)