Connection for subvi and button

[RavensFan]

A local variable is another way you can access the value of a control or indicator.  Find the Stop button terminal on your block diagram, right click and select create local variable.  You can select that variable for reading from or writing to.

This is pretty basic LabVIEW.  I would recommend looking at the online LabVIEW tutorials:
LabVIEW Introduction Course - Three Hours
LabVIEW Introduction Course - Six Hours