...
Expand the Developer Packages folder, find the DemoLabs folder, expand it under the DemoLabs folder, expand the Workflows, right-click on the Activities folder, hover your mouse on the New Activity option and Click on Flow Chart Activity.
Wait for the Form Activity designer to be loaded.
Once the Activity Designer is loaded, go to its properties tab, and from there, search for the System Code Activity. Then, drag and drop it onto the Activity Designer pane.
Now, draw lines to connect your activity with the starting and ending circles. Refer to the image below. and in the Name property give any name say SCActivity