You can extract the ASUS BIOS by using any Unzip tool (WinZip, 7-Zip or WinRAR).
Furthermore you will need a BIOS tool, which is able to modify an AMI Aptio IV UEFI BIOS.
You can find them within the start posts of >this< and >this< thread. The first one is about how to get the customized NVMe Option ROM inserted into the target BIOS.