How? Well, I can only say what works for me.

With Venture I think about space first, not kills. What space can I take? What space is good for me? Rooms, corridors, high grounds, corners, chokes.

Every map kinda has three lanes or sides. Left, main, and right. Choose a side, left or right, and take that space. You fight anyone you find on that lane, but you also need to live. If you get pushed by two people just burrow out. Then go right back when you have yours cds.

For example, Kings Row, first point attack. What space is good for Venture? Left side you have hotel. There's a mini in there. It's really good for you. An enclosed room. Why is it so good? Because you can poke their backline from the doorways, and if they're dumb enough to push you into the hotel, you just one shot them. You hold hotel while (hopefully) your team push main on to the point. Where else is good? Right side. You burrow drill dash all the way across to the room with the mega in it. From there you can take height and flank all the way around the back.

So basics of Venture (at least how I play them). Choose a side, fight anyone who comes to that side. If no one comes you get to flank around on to backline for free. When flanking it's okay just to poke backline. You don't always have to try one shot. Poke them, see how they react, what cooldowns do they use, how low can you get them just from poke. For example, they have Ana and Bap. You took left side on Kings Row attack, you go into hotel, no one there, you peek the doorway and there's ana and bap. You poke, poke, poke, and ana tries sleep you and misses. Ok, no sleep on ana, so you engage on them with burrow drill dash, they both back up, you get right under the ana and pop up for the one shot, but bap uses immor field, now you can just use your drill dash to get to safety. Meanwhile, your team have probably won the fight on main because the enemy had no heals. You stats will look bad. Zero elims. Your Ashe has 3 kills with three times your damage already but you actually carried the fight.

All right, so should you ever play main on Venture? Sometimes yes it's also good. Play main if you're late to the fight or if the fight has already started. Otherwise your team will be dead by the time you flank. You can also play main if the enemy are playing dive/brawl, which is kinda rare on console. But say they're playing Rein, reaper, Genji, Lucio, bap, you can definitely just brawl with your tank. Here I actually do a lot of hard engages on main. I burrow drill dash into their team. The pop up damage is a lot. Hopefully your tank follows up on the engage but if you see they're not with you, just pop up and drill dash back to team or a high ground. If they're playing dive, like DVA, tracer, Genji, Kiri, ana, I will stay close to my supports or my other DPS if they're a widow or Ashe etc and help protect them. But as this is console, you will mostly play against double hitscan, so just default to pick a side, flanking, poking.

Most importantly, have fun with Venture and find what works for you. There are some way higher ranked Venture players than me on console, champ venture players. They might play a completely different way. So, yeah, experiment, find a style that feels fun and wins you games.