If you are new to riding, just ride a lot. Don't worry about intervals or heart rate. Just get lots of time riding all of different terrain around your house. Do some group rides and get a feel for where you need improvement. once you know what you want to work on, build a training plan off that.

For reference, my homemade training plan includes 2-3 SST rides a week, 1 day of hill intervals, 1 day of 1125211 pyramid intervals and 1-2 long (60-70 miles) on the weekends. I wouldn't make a concrete plan like "monday I'm going to ride 2 hours, wednesday 4 hours, etc. etc." as you never know what is going to come up throughout the week. Just figure out what workouts you want to do each week and try your hardest to fit them all in.

Most importantly, don't stress about about missing a workout or two, especially at this time of year. Just try to have fun with it, hopefully you will see some improvement.