The seated calf raise machine targets the leg muscles, in particular the calf or gastrocnemius muscle. The gastrocnemius is the larger calf muscle, forming the main bulge you see when looking at your calf. The soleus is a smaller, flat muscle that lies underneath the gastrocnemius.
First, add an appropriate weight for you at the front of the machine. Once seated the balls of your feet should be resting on the foot platform, adjust the pad so it is secures your legs. Grab the lock bar handle and come slightly up with your feet - this will allow you to set the lock bar down without it dropping.
Once ready to go, grab the handles and begin by lowering the back of your foot downards then come back all the way upwards, repeating - keeping the front of your foot on the rest platform. You should be feeling a stretch each time on the backs of your legs. Once done, place the lock bar back to its original position.