HELP NEEDED : ios 8.1.3 (apple mail app) problems

i tried to add my gmail account to the built in mail app , it refused my password and kept popping up saying : wrong password , although my password is correct ! i've checked my email thought that I might find some security trust mails but i found nothing ! could some one please help me here , I had downloaded gmail app lately and it's working with me perfectly and this is what's making me wonder how is this happening , please technicians help me find out the source of the problem and solve it for Haven's sake ,,