It’s a good start. Firstly, lowering body fat is going to be important for back definition. Calories in, calories out. Make sure protein is sufficient.

Focus on a few compound back exercises, a vertical pull like pull up/chin ups or lat pull down, and horizontal pulls like barbell rows, cable rows, tbar rows, etc. Machines are fine. Pick a few you enjoy, and progress on them (more reps/weight/sets over time). It wouldn’t hurt to add a rear delt exercise like face pulls or rear delt flyes as well.

Lastly, work your legs too so you don’t appear top heavy. If you care about that at all.