Supersets are part of the RepCount Premium package.
Here is how you create a superset:
1: Press the Add Exercise button at the bottom of the workout or routine page.
2: In the switch right above the keyboard, press superset.
3: Select all the exercises that you want to superset
4: When you are done, press the add button in the bottom right corner
Have additional questions. Feel free to reach out at feedback@repcountapp.com