How can i increase shoulder/back strength to lessen clicking from loose joints in shoulders? some movements are restricted.

Do some weights: Do some bench press, lat pulldowns and back extension exercises.

Scapular & cuff work: In order for a shoulder to work well, the scapula (aka shoulder blade) needs to be stable, since it is the base for all shoulder movements. Do exercises that pinch the shoulder blade together in multiple planes. Or better yet, google "scapular stabilizing exercises". Add in rotator cuff strengthening, and you will be doing very well. Focus on low weights and "feel' the muscles.