A very broad question, but i'll do my best to answer it.
The way you approach it will very much depend on your general level of fitness (maybe crossing over from some other sport) and what your cycling goals may be. However you described yourself as a novice, so i'll recommend based on that.
As a novice cyclist, your primary training goal should be gradually increasing time on the bike and building up a large aerobic engine which will serve you well whatever you choose to do with the bike.
Despite having a smart trainer, for the first 4-6 weeks, the most important thing is establishing a pattern of getting on the bike 3-4x a week. Without this pattern (a change of behaviour if you like), its very easy to skip a session or two and then stop. During this period, I would stick to using perceived exertion to measure your efforts.
For the first week start out with relatively easy sessions around effort level 3-5, and then gradually add in 'intervals' of higher intensities. This way you can learn to feel different effort levels and also identify and correct any problems you may have with position on the bike early. During this period TV shows, YouTube, music or any other light distraction is perfect to help the time go by.
After this initial period, you will hopefully have a regular routine established and have more ideas of how to pace yourself at different intensities.
At this point you will be ready to embark on a 'proper' training plan. There are many available either via online platforms such as Zwift or Trainneroad, or from more traditional sources such as British Cycling
Nearly all structured sessions these days should (if they don't pick another one) start out with an FTP test (a particularly unpleasant 20min all out test) to determine the power zones you will use with your smart trainer. From there, Novice/Intermediate plans will likely focus on adding increasingly long intervals between 80-100% of FTP (5-7 RPE).