How to create a mask using binary pixel values of sentinel-1 image

I have used the .img file of a sentinel-1 image and converted it to ascii format using ENVI. Trained it and created a text file of 0s and 1s using python. Now I want to import this file in snap and overlay it as a mask over the original satellite image. The image is rectangle.
I know that I have to somehow use the geocoordinates and use a shape file, this is what i read. Could anyone tell me what exactly I need to do and give some links explaining how to perform it. I could export the file in csv format also, if needed. Finally I will use the mask file to export it as kmz file and overlay the mask in google earth.