Everyone has their own image, even if they want to behave like someone else, but you are the one you see in the mirror every day. If you think the time has come for a change, there is no better time than now to start improving your image.
Steps
Step 1. Think about why you want to change your image
If it's just about being popular, or you fit in with a specific group of people, or because you think someone will like you by changing yourself, don't force yourself. If you want to be more confident, do it now.
Step 2. Define in your mind the image of what you want to look like
How would you describe your current image? How does it make you "feel" the way you present yourself now? How would you "like" to feel? And how can you dress and look to feel that way?
Step 3. Find out the people who own the items you would like to hire
Do you like the toughness of that superhero you saw in that movie? Or the sensuality of that diva you saw at the awards ceremony? Maybe the class and sophistication of old movie stars? You will probably want to mix several images to create one that is tailor-made for you.
Step 4. Take your time
Take it one step at a time. Exaggerations are negative and attention-grabbing, but they don't usually last long. If you want to find your image, you have to build it slowly and lastingly, piece by piece, until one day you look in the mirror before you go out and think, "THIS is me."
Step 5. Stock up your wardrobe
This doesn't mean you have to go out and make up your closet. Just start looking critically at the clothes you have. If every time you pull out that red sweater you hear a voice saying "This" just "isn't me!" then delete it. Replace it with something that "really" fits you, both physically and emotionally. It doesn't have to be new or expensive; you can buy it at a second-hand clothing store, or even recycle your own clothes.
Step 6. Change your attitude
Your physical appearance is only a "part" of your image. If you want to be the embodiment of something (athletic, sophisticated, stylish, smart, etc.). you will not succeed until it appears that you are still living your "old" image.