KPI's are based on sensor readings. The process to create a KPI is as follows:

1. Open the KPI Creator in the Data section. The default view in KPI Creator is to create a new KPI, or you can select an existing KPI from the menu.

2. Name the KPI. 

3. Add the sensors/fields. Select the sensors needed to create the KPI expression.

If you just want to create a graph of a single sensor, select that sensor, and build the expression “=S1”, where S1 is whatever variable is designated to that sensor.