You can use the same squat press machine that you we're already on (adjust weight if needed- I like to go a little bit lighter for these) Start with your feet flat, press through the balls of your feet to elevate your heels. Go slow & controlled, especially on the return motion. Use mind muscle connection to really squeeze your calves the whole time!

*Modification: you can do this standing with dumbbells, or an actual standing calf press machine