Without them, you don't know where you're going, and don't know when you got there.
So set some goals. For example, a 100 km (60 mi) ride by the end of the year.
As Kibbee said, find others to ride with. Ride where you see others ride, stop where they stop, and chat. Or find a local club. Be prepared to move on if the people or club are not meeting your current needs.
It's good to ride with two kinds of riders - ones like you, for friendly competition, and more experienced or faster, to stretch and teach you. And then when you're experienced, ride with less experienced people to pass it on.
I'll add more later ... going for a ride now ... and I'm back.
You'll need to tell us more for us to give detailed advice. We can guess that "Stu" is a guy, and maybe Gen-Y. Or not. We can guess that by training you intend to get seriously into cycling. But we don't know until you tell us. So here is some general advice.
I already mentioned goals.
Have a goal for every ride. I just went on a social Coffee ride - 63 kms to have coffee with friends, at a very relaxed pace. Other rides are training rides, where I might do intervals at a given speed for a given distance, then slow down for a period to recover, and then repeat. Or climb a specific hill some number of times. Some people unkindly call any ride without a goal as junk kilometers or junk miles. See the questions tagged training and performance.
Learn good technique early.
If you are going to do Triathlons then join a Tri club and follow their advice, because Tri riding is quite different to ordinary road cycling.
For road cycling, get a bike computer that shows you your cadence. If you don't already pedal at 90 rpm, then aim for that. Then 100 rpm. Pedaling too slowly causes knee and back problems.
Learn to use your ankles, to help you drive the pedals all the way around the stroke.
Keep your knees in; they should almost touch the top tube on each stroke.
Make sure you have a good riding-position.
Having a professional bike fitting can boost your performance and save you lots of problems later.
Learn some basic skills and techniques.
If you join group rides, be aware that there is etiquette for groups involved.
Increasing your endurance.
Generally, we can increase the distances we ride by about 10% per week. If you work hard on each ride then give your body a day off to recover before the next ride. As you increase the distance, try to maintain your pace. Remember to warm up and cool down properly, and do longer and shorter rides for variation. And check out What is a recovery ride?
Increasing your speed.
This means increasing your power output. You can just ride faster, or climb hills, but the most common way of increasing power is interval training.
Measure what you do.
If you want something to change then measure it. Smartphone apps are one easy way. See Is there an easy to use app for tracking my cycling performance? (iOS or Android) or What is the best way to track your mileage, routes and calories burned?.
Many people use a Garmin device.
If you get serious then learn about VO2 max and diet.
Join a club.
Or more than one. Different clubs can focus on different things, so find one or more that suit you and your goals.