How To do the debug on Thingy91 connected with NRF9160 DK

Dear Sirs.

I bought thing91 and nrf9160.

I have connected the thingy 91 with nrf9160dk with prog/debug cable but I dont able to debug the application on the thingy91. 

The application on debug start always on nrf9160dk

I'm using segger embeedd studio.

Which is the correct sequence to start up.  ? 

Thanks for help

Silvano