You text that person in the same manner you would someone with an iPhone. The difference will be the color. Blue represent an iMessage which are only visible on iOS and OS X devices. Green represent an SMS message which are standard text messages regardless of the mobile phone. Oh, and unless you have an unlimited texting plan, data rates will apply in regard to SMS messages.
Make sure that you are calling a mobile number if you are texting,because if you text a landline and someone answers it, a machine will speak your message,which probably won't be recorded, leaving no way to check your number to reply to you !