I need to change my apple Id. The email I am using for my Id is old and is not working half the time. I need to change my update with a new email for my Apple Id. Please let me know how. Thank you

My apple Id is an old email. The email has been giving me many problems in the last year. The apple Id is used with my phone and streaming Apple TV HD and Itunes. It might be linked with other things such as google but I am not that good with technical side of things so not sure. Many times I can not get into the email or correspond with anyone. I have a different email I would like to make as a new Apple Id for me. Please tell how to go about changing my apple Identification. Thank you. Theresa Giarrosso