how do u remove the image background after adding an alpha channel

What program are you using?

 

I'm not familiar with Gimp. I've always used Photoshop. I don't think an alpha channel is what you want for cutting out the background.

I could tell you what to do in Photoshop but I don't know if it would work in Gimp.

 

I would try invert then cut but I use gimp