I've never ran before, any tips?

My boy is almost 2 years old now and I just got fully equiped to start canicross with him, custom harness, trail running shoes, belt and bungee line.

I've never ran a day in my life, I'm in an okay shape but my cardio is really bad. I want to work on that for my health and just because I've always wanted to try it out.

Any tips for a complete beginner? Or good ressources I could look into?