Open program and click to 'Flash from file'.
What you need to do is to throw the EFI folder into the EFI partition created after writing the image to your USB memory. Since there is no EFI in the image yet, I will update it externally with the image every month.
If you report the problems you encounter as feedback, I can fix my problems. Today, I present to all of you the solidified OpenCore Bootloader and the OSX images I have prepared. This repo contains the image and global EFI needed to install macOS on your compatible computer.