First an important note: V brakes require different levers. If your bike had cantilevers, it had standard pull levers. Those are unsafe to use with V brakes. They bottom out very easily with V brakes and if you can run them with minimal pad gap, the stopping force is dangerously high unless flex prevents you from applying the brakes with full force (usually it does so). So, use V brake specific levers on V brakes.
I suspect your problem is that the springs have some configuration issues. When you installed the brakes, did you ensure that on both sides, the spring is on the same hole? Usually there are 3 holes.
The fine tuning can be done with the adjustment screws on either side but they fail to provide enough adjustment if the springs are in different holes.
So, I suggest:
- Update your question by posting a picture that shows into which holes the springs go
- Update your question by posting a picture that shows how you installed the cable (it may be you misunderstood something about installing the cable). You do have a "noodle" for the cable, don't you? (Because the picture has no cable, I can't see if you use the correct noodle)