Lose weight, increase your power.
When you talk about hills, do you mean rollers (a few hundred yards long with <1000 ft elevation change) or long sustained climbs (distance in miles, elevation measured in 1000’s)?
Many big guys can ride rollers, since they’re basically a short sprint. Big guys tend to generate a lot of power so they can just crank up these hills for short periods. IMO, this isn’t “climbimg.”
Most big guys get killed on long sustained climbs. They just don’t have a high power to weight ratio that they can sustain at a relatively low effort.
So… If you want to get stronger on rollers, you need to increase your peak power. Hill repeats, sprints, interval work will help. Personally I don’t like structured workouts. Another thing you can do is just hammer every roller you encounter on an otherwise easy ride.
To get better at long climbs, you will need to become more efficient. Drop some weight (Unless you’re like 6’7"), and ride a lot. You’ll still need to increase your power output but not specifically your peak power. How to do this? Well, I’m at a loss. For me (when I’m in shape, which I’m not), I ride a lot, ride a lot of hills, ride with groups who are faster than me, ride into the wind, always pull if I’m riding in a group that’s slower than me. But just ride.
BTW, what I recommend for riding rollers fast isn’t necessarily the best thing to do for Triathlon riding. Any really hard effort on the bike will impact your run. For racing tris, you generally want to ride at a consistent power output that you can sustain over the length of the course. Hammering up hills will hurt you on the run.
Honestly, two things jump out at me from your post “I’m a newer cyclist”, and “I weigh 210” or so. Getting strong on hills and in the wind takes time and miles in your legs. Losing weight only helps. BTW I’m not bagging on you for the weight thing, I’m currently tipping the scales at just under 220.