You can customize your character by clicking your inventory. You can find you’re your inventory by clicking the bag icon on the top of your screen.  On the right column you’ll see your current character customizations.

Gender & Skin tone
Click the Female or Male button to change your gender
Choose your preferred skin tone by checkin the color palet below your character

Outfit color
Click the shirt icon to see your available shirt colors. Select a shirt to change the color.
To buy new colors go to the outfit shop. You can find the button on the top left of the inventory.
Outfit shop > Pins > Shirts

Hats
Click the hat icon and select a hat from your collection. You can scroll down to see all the hats you’ve collected over time.  Select the hat you would like to wear.

You can buy new hats in the outfit shop. Outfit shop > hats 
On the bottom you’ll vind tabs to select hats from different areas of the game

Pins
Click the flag icon to find the pins you’ve collected. Just click the pin you like to costomize your character. 
You can buy new pins in the Outfit shop > Pins