Blending alpha in opengl es 2.0

Blending alpha in opengl es 2.0

I try blending alpha of two textures. First texture it some image, second
texture this is rectangle with transparent round in center. I need mix
this two textures so that in result I my background with transperent round
in center. For this, I try to use glBlendFunc, but I was able to get only
the whole transparent background, in other words, all of my background
became transparent. How can I mixed alpha of textures via glBlendFunc?