Google "theory of cycling training." That's a good start. Read everything on the first couple of pages. Caution: there are many ways to get about the same result. There's not one system. That makes it confusing, but it's also a good thing, i.e. ride lots and you'll get there, no matter how you do it. Volume and hills works, as do elaborate structured plans. Also, there are many things riders train for. It's good to have a goal to shape your training around.
The basic ides, even with just riding lots, is that you want to push yourself hard, but not too hard. You want to get tired but not too tired. You want a mix of hard and easy rides, with more time spent easy than hard. This is common to most training plans. I think the most important thing I can pass on is to establish some metrics for yourself so you can tell what's happening with your body.
The simplest thing, since you have HR, is to know what your HR is when climbing as hard as you can for several minutes, say 5 minutes of steady hard effort. Then if you go out for a ride and on your first climb after warming up, your HR simply won't come up no matter how hard you push - you are overtired. Ride easy for a couple days until your HR comes up normally.
For 25 years, I've taken my morning resting and resting standing HR. I get up and pee, then lie down with my transmitter strap on, rest for a few minutes until my HR stops dropping, then watch it for maybe 3 minutes. Remember that HR. Stand up and watch your HR for about 3 minutes. Remember what your HR seems to average for about the last 30". Keep track of these numbers somewhere. If your MRHR gets to be 6-8 beats higher than normal, you have to rest. If the difference between your MRHR and MSHR increases by 10 more than normal, you have to rest. Using these metrics, you can walk the knife edge between training hard and overtraining with confidence. BTW hitting those high numbers and then resting is not a bad thing - it's actually a good thing, a goal really. That's overreaching and you want that stress. During the following rest period, you get stronger.
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Results matter