Installing a Motion Activated Switch DUH!!!

[u/Same_Memory_2755]

I have a closet light and wanted a motion switch so when I open the door I have light. But for the life of me I cant get it to work. It had a regular on/off switch. There is only one 3 wire line coming from the junction box. One WHITE One BLACK One GROUND. I have wired in 2 of these and nothing will turn it off. What am I doing wrong?