If you want some high intensity you’ll need to choose a shorter focus duration. Eg climber or GC specialist
You can increase threshold from the bottom via low intensity (and would suggest that’s still the bulk of training - aim should be a very high training load too), but at times it’s good to raise the ceiling with some high intensity, and most coaches would prescribe some.
Similar question has come up before eg here, and here and you can search the forum for others… but that’s the gist of it 
As an aside, if you’re v new to Xert, they have a series of videos as well as podcasts which give more tips for getting the most out if it