from your pic you have a nice athletic body. It won´t be too hard to get a more muscular body.
Lift intelligently (not too often, with correct form, using weight you can do the exercise correctly with, with intensity and focus, working the whole body and developing opposing muscles in a balanced way),
eat well (frequently, smaller portions, lower fat, no processed and refined foods and crap, high protein, complex carbs),
rest well (8 hours sleep a night, days off).
3 months will give you a noticable difference, a year and you´ll have a new body. You don´t need to lift more than 3 times a week to start with. Once you start to lift more than that you have to be careful not to over train. THis is why some people do splits. You do not need them until you are training 4 plus days a week. You really need to find a GOOD trainer or experienced lifter to show you correct form otherwise you will not be using your energy in the gym to most effect.
Look at my private pics and you´ll see what I mean
BTW self confidence is only loosely related to how you look. There are people who look terrible who have lots of it, and people who look amazing who have none at all .