How do I get a positive self-concept?

Be a Good Person. There are many ways to have healthy self-esteem. Most agree that there are two broad components to self-esteem: (1) the view that I am a worthwhile or good person; and (2) the view that I have some competence (i know things or know how to do things). If people continue to strive to be virtuous or good and to learn and develop skills they will tend to have a positive self-concept. Striving is key.
Long Jorney. You can do an inventory of the things you consider positive about you (ho matter how small these things might seem), you can also start by identifying things you do well (anything positive), and build up from there. Doing positive affirmation, creating a goal list for the day and seeing what you've achieved will help you with sense of accomplishment, leading to more positive sense of self.