You can change your password by going in your profile and click on the button "Change Password."
A window will appear where you will have to fill your "Old Password" and type twice your "New Password."
Make sure that you remember your password or use a password manager.
Above all, make sure that your password is not something easy.
You can test here, the strength of your password.
This video is extremely informative if you are not sure how to create a strong password:
Tip: Do not share your password with ANYONE.