I know it's always a problem for lots of women to lose wieght but in my case I want to gain weight... I eat a lot of junk food but it doesn't work!! Wats the most quick way??

Okay, stop eating the junk food now!
Eat nutritious foods that are high in calories. Examples are whole-grain breads, vegetables such as avocados and potatoes, kidney beans, lean red meat, poultry and fish.
Increase the caloric value of your meals. Like add chopped meat to your pasta sauce.
Avoid skipping meals. Eat three meals a day and at least two snacks.
Increase your normal portion size. Take a second scoop of pasta, or add two bananas to your oatmeal.
Choose higher-calorie foods when given a choice. For example, corn is higher in calories than green beans.
Relax - excessive fidgeting and restlessness can burn up a lot of calories.
Add weight lifting to your exercise program. It helps build muscle mass.
Tips & Warnings
You should have a doctor rule out any physical problems, such as hormonal imbalances, if you cannot seem to put on any weight.
Although it seems like a logical way to bulk up, avoid adding excess fat and sweets to your diet. Eat fats and oils in moderation; they should account for no more than 30 percent of your total caloric intake.
Good luck!