Hi,
I would say cross-traning is very important if you have a long term commitment with running. You have to create training habits, that's where cross-training comes handy, both when you are a beginner runner, or when you come back from injury.
Set a weekly training schedule that you can sustain regularly, and fill it with as much running as you can do safely. The rest, do cross-training, even go out for a walk. What you do in your training will, of course, depend on your current ability. At the beginning you need to build your aerobic base, so lots of easy running, and easy x-training. Later, when you are a bit stronger, you can start developing your strength/endurance. At the beginning, probably it's easier to do it in cross-training to avoid bigger impact forces. Little by little, transition from cross-training to running.