Activity selection with Garmin watch

RockingWithLJ

I have a vivoactive 3 and I'm doing Autumn calabrese's 80-day Obsession through Beachbody. Currently I'm selecting cardio to do the workouts because the strength training is too involved and doesn't reflect the sets that I actually need it to reflect. I also noticed that it doesn't track my heart rate very well either.
I want to try to create a manual activity but not fully understanding the steps and how to do that through connect and Consulting Google has led me nowhere
Has anyone created a manual activity? If not, do you have a go-to option for all activities for ease?