Talk to your doctor about what day to start using the patch. It is usually recommended that the first patch be placed on the first day of your next menstrual period. If the patch is started on any other day, use a backup method of birth control for 7 days. Start the patch on a day that is easy to remember.

How does it work?
There are many drugs which can be delivered thru the skin and achieve the same or better benefit to the body. The birth control patch is one of these products.
The patch, which contains the active ingredients in a birth control pill (estrogen and progestin), delivers continuous levels of hormones to your system thru your skin. The patch works exactly like a birth control pill to prevent pregnancy: thickens mucus in the genital tract, prevents the formation of eggs and prevents ovulation.
In some women who find taking the birth control pill daily difficult, the patch can offer more effective pregnancy prevention and menstrual control. The patch can be 97-99% effective in preventing pregnancy

Where do i put it?
You have 4 choices: the lower abdomen, buttocks, upper, outer arm or back of the shoulder. The patch should never be applied to the chest or breasts
To ensure the effectiveness of ORTHO EVRA®, do not place the Patch on areas of your skin where makeup, lotions, creams, powders or other products are or will be applied. In addition, do not place ORTHO EVRA® on skin that is red, irritated or cut.
Women change the location of the patch weekly to avoid skin irritation and enable you to remove the adhesive from the old site.

advantages:
The patch is more effective for preventing pregnancy than barrier methods of birth control, such as the condom or diaphragm.
It may reduce acne, heavy bleeding and cramping, and symptoms of premenstrual syndrome.
It's convenient. You put it on only 3 times each month. You do not have to interrupt sex to protect against pregnancy.
It's easy to check to see if you forgot to put one on.

disadvantages:
The patch doesn't protect against sexually transmitted infections (STIs), such as herpes or HIV/AIDS. If you aren't sure if your sex partner might have an STI, use a condom to protect against disease.
The patch may cause changes in your period. You may miss periods, or you may have spotting or a little bleeding. If you miss a period, find out if you are pregnant.
It may cause mood changes, less interest in sex, or weight gain.
The patch contains estrogen. It may not be right for you if you have certain health problems or concerns.
It may increase your risk of blood clots.
It may be less effective in women who are overweight.
You must remember to change the patch on schedule.



References:
Birth Control Hormones: The Patch - Women's Health - Lake Shore Obstetrics and Gynecology - Chicago, Illinois | Preventive Care - Endometrial Ablation - Essure - Tubal Ligation - da Vinci Robotic Surgery
Birth Control: How to Use the Patch - Pacific Gynecology Specialists Seattle | Kirkland, Issaquah, Seattle, Bellevue, Renton, WA
Birth Control Patch - Paradise Valley OBGYN | OB/GYN Scottsdale, Arizona