Well, soul searching means looking inside yourself and deciding if the person you are or are becoming is the person you really want to be. Get a journal, that's always a good start. Think about your past and your future. What events and people, both good and bad, have made you who you are? Who are you, and are you happy with who you are and how your life is going? Who do you want to become and what do you want to accomplish in life? Will the life you're leading now lead you to those goals? If you get lost, or don't have the answers to these questions, don't worry, that's normal. Think about it as you go about your life. Examine the things you do and say and your reasons for them, then write these down. The more you think and write, the more you'll come to understand yourself.
Then you can start making plans. What things about yourself or your life do you want to change? What influences do you want to cut out and which ones do you want to increase? Are there bad habits you want to get rid of and good ones you want to put in their place? What things do you need to do to reach your goals? It sounds like you have some good friends who want the best for you, talk to them about it. Ask them what your good points and your bad points are and what they think you can improve. Try not to be too sensitive to their answers, they want to help you.
As you go through this process, you may come up against roadblocks, things you can't seem to change no matter how hard you try. If this happens, you may need to seek out professional help to get over them; there's nothing shameful about this, most people need help at some point in their life.
With thought, planning, and action, and some help from your friends, your life will be happier than you can imagine.